21564961907 has 16 divisors (see below), whose sum is σ = 23038916832. Its totient is φ = 20114588160.

The previous prime is 21564961903. The next prime is 21564961931. The reversal of 21564961907 is 70916946512.

It is a cyclic number.

It is not a de Polignac number, because 21564961907 - 2² = 21564961903 is a prime.

It is a super-2 number, since 2×21564961907² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21564961903) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 920732 + ... + 943862.

It is an arithmetic number, because the mean of its divisors is an integer number (1439932302).

Almost surely, 2^21564961907 is an apocalyptic number.

21564961907 is a deficient number, since it is larger than the sum of its proper divisors (1473954925).

21564961907 is a wasteful number, since it uses less digits than its factorization.

21564961907 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23638.

The product of its (nonzero) digits is 816480, while the sum is 50.

The spelling of 21564961907 in words is "twenty-one billion, five hundred sixty-four million, nine hundred sixty-one thousand, nine hundred seven".