21131523547 has 2 divisors, whose sum is σ = 21131523548. Its totient is φ = 21131523546.

The previous prime is 21131523503. The next prime is 21131523551. The reversal of 21131523547 is 74532513112.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21131523547 is a prime.

It is a super-2 number, since 2×21131523547² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21131523557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10565761773 + 10565761774.

It is an arithmetic number, because the mean of its divisors is an integer number (10565761774).

Almost surely, 2^21131523547 is an apocalyptic number.

21131523547 is a deficient number, since it is larger than the sum of its proper divisors (1).

21131523547 is an equidigital number, since it uses as much as digits as its factorization.

21131523547 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 25200, while the sum is 34.

The spelling of 21131523547 in words is "twenty-one billion, one hundred thirty-one million, five hundred twenty-three thousand, five hundred forty-seven".