20691399456 has 720 divisors, whose sum is σ = 79370432064. Its totient is φ = 5169858048.

The previous prime is 20691399433. The next prime is 20691399479. The reversal of 20691399456 is 65499319602.

20691399456 is a `hidden beast` number, since 206 + 9 + 1 + 399 + 45 + 6 = 666.

It is an interprime number because it is at equal distance from previous prime (20691399433) and next prime (20691399479).

It is a super-2 number, since 2×20691399456² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 119 ways as a sum of consecutive naturals, for example, 1089021015 + ... + 1089021033.

Almost surely, 2^20691399456 is an apocalyptic number.

20691399456 is a gapful number since it is divisible by the number (26) 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 20691399456, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39685216032).

20691399456 is an abundant number, since it is smaller than the sum of its proper divisors (58679032608).

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

20691399456 is an frugal number, since it uses more digits than its factorization.

20691399456 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 95 (or 44 counting only the distinct ones).

The product of its (nonzero) digits is 3149280, while the sum is 54.

Adding to 20691399456 its product of nonzero digits (3149280), we get a square (20694548736 = 143856²).

The spelling of 20691399456 in words is "twenty billion, six hundred ninety-one million, three hundred ninety-nine thousand, four hundred fifty-six".