21152251531 has 4 divisors (see below), whose sum is σ = 21196411200. Its totient is φ = 21108091864.

The previous prime is 21152251529. The next prime is 21152251567. The reversal of 21152251531 is 13515225112.

It is a happy number.

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 21152251531 - 2¹ = 21152251529 is a prime.

It is a super-2 number, since 2×21152251531² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21152251531.

It is not an unprimeable number, because it can be changed into a prime (21152251831) 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, 22079116 + ... + 22080073.

It is an arithmetic number, because the mean of its divisors is an integer number (5299102800).

Almost surely, 2^21152251531 is an apocalyptic number.

21152251531 is a deficient number, since it is larger than the sum of its proper divisors (44159669).

21152251531 is an equidigital number, since it uses as much as digits as its factorization.

21152251531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44159668.

The product of its digits is 3000, while the sum is 28.

Adding to 21152251531 its reverse (13515225112), we get a palindrome (34667476643).

The spelling of 21152251531 in words is "twenty-one billion, one hundred fifty-two million, two hundred fifty-one thousand, five hundred thirty-one".