21561131007 has 48 divisors (see below), whose sum is σ = 34330470720. Its totient is φ = 12959046144.

The previous prime is 21561131003. The next prime is 21561131057. The reversal of 21561131007 is 70013116512.

21561131007 is a `hidden beast` number, since 2 + 15 + 611 + 31 + 0 + 0 + 7 = 666.

It is not a de Polignac number, because 21561131007 - 2² = 21561131003 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21561131003) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 867469 + ... + 891977.

It is an arithmetic number, because the mean of its divisors is an integer number (715218140).

Almost surely, 2^21561131007 is an apocalyptic number.

21561131007 is a deficient number, since it is larger than the sum of its proper divisors (12769339713).

21561131007 is a wasteful number, since it uses less digits than its factorization.

21561131007 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24704 (or 24701 counting only the distinct ones).

The product of its (nonzero) digits is 1260, while the sum is 27.

Adding to 21561131007 its reverse (70013116512), we get a palindrome (91574247519).

The spelling of 21561131007 in words is "twenty-one billion, five hundred sixty-one million, one hundred thirty-one thousand, seven".