21261642513 has 4 divisors (see below), whose sum is σ = 28348856688. Its totient is φ = 14174428340.

The previous prime is 21261642487. The next prime is 21261642517. The reversal of 21261642513 is 31524616212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21261642513 - 2⁵ = 21261642481 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21261642517) 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, 3543607083 + ... + 3543607088.

It is an arithmetic number, because the mean of its divisors is an integer number (7087214172).

Almost surely, 2^21261642513 is an apocalyptic number.

It is an amenable number.

21261642513 is a deficient number, since it is larger than the sum of its proper divisors (7087214175).

21261642513 is an equidigital number, since it uses as much as digits as its factorization.

21261642513 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7087214174.

The product of its digits is 17280, while the sum is 33.

The spelling of 21261642513 in words is "twenty-one billion, two hundred sixty-one million, six hundred forty-two thousand, five hundred thirteen".