21511505131 has 4 divisors (see below), whose sum is σ = 22253281200. Its totient is φ = 20769729064.

The previous prime is 21511505117. The next prime is 21511505143. The reversal of 21511505131 is 13150511512.

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 21511505131 - 2²⁵ = 21477950699 is a prime.

It is a super-2 number, since 2×21511505131² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21511505096 and 21511505105.

It is not an unprimeable number, because it can be changed into a prime (21511506131) 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, 370887991 + ... + 370888048.

It is an arithmetic number, because the mean of its divisors is an integer number (5563320300).

Almost surely, 2^21511505131 is an apocalyptic number.

21511505131 is a deficient number, since it is larger than the sum of its proper divisors (741776069).

21511505131 is an equidigital number, since it uses as much as digits as its factorization.

21511505131 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 741776068.

The product of its (nonzero) digits is 750, while the sum is 25.

The spelling of 21511505131 in words is "twenty-one billion, five hundred eleven million, five hundred five thousand, one hundred thirty-one".