21560535981 has 6 divisors (see below), whose sum is σ = 31142996430. Its totient is φ = 14373690648.

The previous prime is 21560535979. The next prime is 21560535989. The reversal of 21560535981 is 18953506512.

21560535981 is a `hidden beast` number, since 2 + 1 + 5 + 6 + 0 + 53 + 598 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 19364114025 + 2196421956 = 139155^2 + 46866^2 .

It is not a de Polignac number, because 21560535981 - 2¹ = 21560535979 is a prime.

It is a super-2 number, since 2×21560535981² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21560535989) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1197807546 + ... + 1197807563.

It is an arithmetic number, because the mean of its divisors is an integer number (5190499405).

Almost surely, 2^21560535981 is an apocalyptic number.

It is an amenable number.

21560535981 is a deficient number, since it is larger than the sum of its proper divisors (9582460449).

21560535981 is a wasteful number, since it uses less digits than its factorization.

21560535981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2395615115 (or 2395615112 counting only the distinct ones).

The product of its (nonzero) digits is 324000, while the sum is 45.

The spelling of 21560535981 in words is "twenty-one billion, five hundred sixty million, five hundred thirty-five thousand, nine hundred eighty-one".