20643244651 has 4 divisors (see below), whose sum is σ = 21123320152. Its totient is φ = 20163169152.

The previous prime is 20643244603. The next prime is 20643244691. The reversal of 20643244651 is 15644234602.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20643244651 - 2²⁵ = 20609690219 is a prime.

It is a super-2 number, since 2×20643244651² (a number of 21 digits) contains 22 as substring.

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 20643244651.

It is not an unprimeable number, because it can be changed into a prime (20643244691) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 240037686 + ... + 240037771.

It is an arithmetic number, because the mean of its divisors is an integer number (5280830038).

Almost surely, 2^20643244651 is an apocalyptic number.

20643244651 is a deficient number, since it is larger than the sum of its proper divisors (480075501).

20643244651 is an equidigital number, since it uses as much as digits as its factorization.

20643244651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 480075500.

The product of its (nonzero) digits is 138240, while the sum is 37.

The spelling of 20643244651 in words is "twenty billion, six hundred forty-three million, two hundred forty-four thousand, six hundred fifty-one".