21131657251 has 4 divisors (see below), whose sum is σ = 21266253952. Its totient is φ = 20997060552.

The previous prime is 21131657249. The next prime is 21131657269. The reversal of 21131657251 is 15275613112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21131657251 - 2¹ = 21131657249 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21131651251) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 67298115 + ... + 67298428.

It is an arithmetic number, because the mean of its divisors is an integer number (5316563488).

Almost surely, 2^21131657251 is an apocalyptic number.

21131657251 is a deficient number, since it is larger than the sum of its proper divisors (134596701).

21131657251 is a wasteful number, since it uses less digits than its factorization.

21131657251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 134596700.

The product of its digits is 12600, while the sum is 34.

The spelling of 21131657251 in words is "twenty-one billion, one hundred thirty-one million, six hundred fifty-seven thousand, two hundred fifty-one".