21513511231 has 2 divisors, whose sum is σ = 21513511232. Its totient is φ = 21513511230.

The previous prime is 21513511199. The next prime is 21513511241. The reversal of 21513511231 is 13211531512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21513511231 - 2⁵ = 21513511199 is a prime.

It is a super-2 number, since 2×21513511231² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21513511196 and 21513511205.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21513511241) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10756755615 + 10756755616.

It is an arithmetic number, because the mean of its divisors is an integer number (10756755616).

Almost surely, 2^21513511231 is an apocalyptic number.

21513511231 is a deficient number, since it is larger than the sum of its proper divisors (1).

21513511231 is an equidigital number, since it uses as much as digits as its factorization.

21513511231 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 900, while the sum is 25.

The spelling of 21513511231 in words is "twenty-one billion, five hundred thirteen million, five hundred eleven thousand, two hundred thirty-one".