21161560251 has 96 divisors (see below), whose sum is σ = 33984437760. Its totient is φ = 11589101568.

The previous prime is 21161560243. The next prime is 21161560279. The reversal of 21161560251 is 15206516112.

It is not a de Polignac number, because 21161560251 - 2³ = 21161560243 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21161560351) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 90822031 + ... + 90822263.

It is an arithmetic number, because the mean of its divisors is an integer number (354004560).

Almost surely, 2^21161560251 is an apocalyptic number.

21161560251 is a deficient number, since it is larger than the sum of its proper divisors (12822877509).

21161560251 is a wasteful number, since it uses less digits than its factorization.

21161560251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 437 (or 364 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 30.

The spelling of 21161560251 in words is "twenty-one billion, one hundred sixty-one million, five hundred sixty thousand, two hundred fifty-one".