21115013531 has 2 divisors, whose sum is σ = 21115013532. Its totient is φ = 21115013530.

The previous prime is 21115013503. The next prime is 21115013537. The reversal of 21115013531 is 13531051112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21115013531 - 2⁶ = 21115013467 is a prime.

It is a super-2 number, since 2×21115013531² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21115013497 and 21115013506.

It is not a weakly prime, because it can be changed into another prime (21115013537) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10557506765 + 10557506766.

It is an arithmetic number, because the mean of its divisors is an integer number (10557506766).

Almost surely, 2^21115013531 is an apocalyptic number.

21115013531 is a deficient number, since it is larger than the sum of its proper divisors (1).

21115013531 is an equidigital number, since it uses as much as digits as its factorization.

21115013531 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 450, while the sum is 23.

Adding to 21115013531 its reverse (13531051112), we get a palindrome (34646064643).

The spelling of 21115013531 in words is "twenty-one billion, one hundred fifteen million, thirteen thousand, five hundred thirty-one".