21315013920 has 240 divisors, whose sum is σ = 77819547960. Its totient is φ = 5487906816.

The previous prime is 21315013901. The next prime is 21315013921. The reversal of 21315013920 is 2931051312.

21315013920 is a `hidden beast` number, since 2 + 131 + 501 + 3 + 9 + 20 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 18586414224 + 2728599696 = 136332^2 + 52236^2 .

It is a tau number, because it is divible by the number of its divisors (240).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21315013921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 347484 + ... + 404196.

Almost surely, 2^21315013920 is an apocalyptic number.

21315013920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21315013920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38909773980).

21315013920 is an abundant number, since it is smaller than the sum of its proper divisors (56504534040).

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

21315013920 is a wasteful number, since it uses less digits than its factorization.

21315013920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56769 (or 56752 counting only the distinct ones).

The product of its (nonzero) digits is 1620, while the sum is 27.

The spelling of 21315013920 in words is "twenty-one billion, three hundred fifteen million, thirteen thousand, nine hundred twenty".