21321555715 has 4 divisors (see below), whose sum is σ = 25585866864. Its totient is φ = 17057244568.

The previous prime is 21321555707. The next prime is 21321555721. The reversal of 21321555715 is 51755512312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21321555715 - 2³ = 21321555707 is a prime.

It is a super-2 number, since 2×21321555715² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2132155567 + ... + 2132155576.

It is an arithmetic number, because the mean of its divisors is an integer number (6396466716).

Almost surely, 2^21321555715 is an apocalyptic number.

21321555715 is a deficient number, since it is larger than the sum of its proper divisors (4264311149).

21321555715 is an equidigital number, since it uses as much as digits as its factorization.

21321555715 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4264311148.

The product of its digits is 52500, while the sum is 37.

The spelling of 21321555715 in words is "twenty-one billion, three hundred twenty-one million, five hundred fifty-five thousand, seven hundred fifteen".