21640662451 has 8 divisors (see below), whose sum is σ = 22129052400. Its totient is φ = 21156325920.

The previous prime is 21640662443. The next prime is 21640662493. The reversal of 21640662451 is 15426604612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21640662451 - 2³ = 21640662443 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21640662451.

It is not an unprimeable number, because it can be changed into a prime (21640662401) 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 7 ways as a sum of consecutive naturals, for example, 1002556 + ... + 1023913.

It is an arithmetic number, because the mean of its divisors is an integer number (2766131550).

Almost surely, 2^21640662451 is an apocalyptic number.

21640662451 is a deficient number, since it is larger than the sum of its proper divisors (488389949).

21640662451 is a wasteful number, since it uses less digits than its factorization.

21640662451 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2026709.

The product of its (nonzero) digits is 69120, while the sum is 37.

The spelling of 21640662451 in words is "twenty-one billion, six hundred forty million, six hundred sixty-two thousand, four hundred fifty-one".