21131312837491 has 4 divisors (see below), whose sum is σ = 21131324581752. Its totient is φ = 21131301093232.

The previous prime is 21131312837471. The next prime is 21131312837507. The reversal of 21131312837491 is 19473821313112.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21131312837491 - 2⁷ = 21131312837363 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21131312837471) 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, 2544706 + ... + 6981271.

It is an arithmetic number, because the mean of its divisors is an integer number (5282831145438).

Almost surely, 2^{21131312837491} is an apocalyptic number.

21131312837491 is a deficient number, since it is larger than the sum of its proper divisors (11744261).

21131312837491 is an equidigital number, since it uses as much as digits as its factorization.

21131312837491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11744260.

The product of its digits is 217728, while the sum is 46.

The spelling of 21131312837491 in words is "twenty-one trillion, one hundred thirty-one billion, three hundred twelve million, eight hundred thirty-seven thousand, four hundred ninety-one".