20991691392 has 128 divisors (see below), whose sum is σ = 67473440640. Its totient is φ = 5644812288.

The previous prime is 20991691351. The next prime is 20991691411. The reversal of 20991691392 is 29319619902.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (128).

It is a super-2 number, since 2×20991691392² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (51).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 183993 + ... + 275384.

It is an arithmetic number, because the mean of its divisors is an integer number (527136255).

Almost surely, 2^20991691392 is an apocalyptic number.

It is an amenable number.

20991691392 is an abundant number, since it is smaller than the sum of its proper divisors (46481749248).

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

20991691392 is a wasteful number, since it uses less digits than its factorization.

20991691392 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 459418 (or 459406 counting only the distinct ones).

The product of its (nonzero) digits is 472392, while the sum is 51.

The spelling of 20991691392 in words is "twenty billion, nine hundred ninety-one million, six hundred ninety-one thousand, three hundred ninety-two".