20991498395904 has 135 divisors (see below), whose sum is σ = 62594817325117. Its totient is φ = 6996946212864.

The previous prime is 20991498395887. The next prime is 20991498395911. The reversal of 20991498395904 is 40959389419902.

The square root of 20991498395904 is 4581648.

It is a perfect power (a square), and thus also a powerful number.

20991498395904 is a `hidden beast` number, since 2 + 0 + 9 + 9 + 149 + 8 + 395 + 90 + 4 = 666.

It can be written as a sum of positive squares in only one way, i.e., 18830739513600 + 2160758882304 = 4339440^2 + 1469952^2 .

It is a super-3 number, since 3×20991498395904³ (a number of 41 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (72).

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 14 ways as a sum of consecutive naturals, for example, 659741404 + ... + 659773220.

Almost surely, 2^{20991498395904} is an apocalyptic number.

20991498395904 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

20991498395904 is the 4581648-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20991498395904

20991498395904 is an abundant number, since it is smaller than the sum of its proper divisors (41603318929213).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20991498395904 is an frugal number, since it uses more digits than its factorization.

20991498395904 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 63662 (or 31822 counting only the distinct ones).

The product of its (nonzero) digits is 226748160, while the sum is 72.

The spelling of 20991498395904 in words is "twenty trillion, nine hundred ninety-one billion, four hundred ninety-eight million, three hundred ninety-five thousand, nine hundred four".