21320647821 has 96 divisors (see below), whose sum is σ = 36933142400. Its totient is φ = 12111897600.

The previous prime is 21320647771. The next prime is 21320647861. The reversal of 21320647821 is 12874602312.

It is a happy number.

21320647821 is a `hidden beast` number, since 2 + 1 + 3 + 2 + 0 + 647 + 8 + 2 + 1 = 666.

It is not a de Polignac number, because 21320647821 - 2²² = 21316453517 is a prime.

It is a super-2 number, since 2×21320647821² (a number of 21 digits) contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21320647861) 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 95 ways as a sum of consecutive naturals, for example, 6019311 + ... + 6022851.

Almost surely, 2^21320647821 is an apocalyptic number.

It is an amenable number.

21320647821 is a deficient number, since it is larger than the sum of its proper divisors (15612494579).

21320647821 is a wasteful number, since it uses less digits than its factorization.

21320647821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3688 (or 3671 counting only the distinct ones).

The product of its (nonzero) digits is 32256, while the sum is 36.

The spelling of 21320647821 in words is "twenty-one billion, three hundred twenty million, six hundred forty-seven thousand, eight hundred twenty-one".