21517056023 has 4 divisors (see below), whose sum is σ = 21545037360. Its totient is φ = 21489074688.

The previous prime is 21517056019. The next prime is 21517056031. The reversal of 21517056023 is 32065071512.

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 21517056023 - 2² = 21517056019 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21517056053) 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, 13989515 + ... + 13991052.

It is an arithmetic number, because the mean of its divisors is an integer number (5386259340).

Almost surely, 2^21517056023 is an apocalyptic number.

21517056023 is a deficient number, since it is larger than the sum of its proper divisors (27981337).

21517056023 is an equidigital number, since it uses as much as digits as its factorization.

21517056023 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27981336.

The product of its (nonzero) digits is 12600, while the sum is 32.

The spelling of 21517056023 in words is "twenty-one billion, five hundred seventeen million, fifty-six thousand, twenty-three".