21456763921 has 4 divisors (see below), whose sum is σ = 21620556144. Its totient is φ = 21292971700.

The previous prime is 21456763883. The next prime is 21456764027. The reversal of 21456763921 is 12936765412.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21456763921 - 2¹¹ = 21456761873 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21456763121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 81895915 + ... + 81896176.

It is an arithmetic number, because the mean of its divisors is an integer number (5405139036).

Almost surely, 2^21456763921 is an apocalyptic number.

It is an amenable number.

21456763921 is a deficient number, since it is larger than the sum of its proper divisors (163792223).

21456763921 is a wasteful number, since it uses less digits than its factorization.

21456763921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 163792222.

The product of its digits is 544320, while the sum is 46.

The spelling of 21456763921 in words is "twenty-one billion, four hundred fifty-six million, seven hundred sixty-three thousand, nine hundred twenty-one".