21767621521 has 8 divisors (see below), whose sum is σ = 22808294784. Its totient is φ = 20734802880.

The previous prime is 21767621507. The next prime is 21767621539. The reversal of 21767621521 is 12512676712.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21767621521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21767621591) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1957981 + ... + 1969066.

It is an arithmetic number, because the mean of its divisors is an integer number (2851036848).

Almost surely, 2^21767621521 is an apocalyptic number.

It is an amenable number.

21767621521 is a deficient number, since it is larger than the sum of its proper divisors (1040673263).

21767621521 is a wasteful number, since it uses less digits than its factorization.

21767621521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3927311.

The product of its digits is 70560, while the sum is 40.

The spelling of 21767621521 in words is "twenty-one billion, seven hundred sixty-seven million, six hundred twenty-one thousand, five hundred twenty-one".