21556023 has 4 divisors (see below), whose sum is σ = 28741368. Its totient is φ = 14370680.

The previous prime is 21556021. The next prime is 21556027. The reversal of 21556023 is 32065512.

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 21556023 - 2¹ = 21556021 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21555984 and 21556002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21556021) 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, 3592668 + ... + 3592673.

It is an arithmetic number, because the mean of its divisors is an integer number (7185342).

Almost surely, 2^21556023 is an apocalyptic number.

21556023 is a deficient number, since it is larger than the sum of its proper divisors (7185345).

21556023 is an equidigital number, since it uses as much as digits as its factorization.

21556023 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7185344.

The product of its (nonzero) digits is 1800, while the sum is 24.

The square root of 21556023 is about 4642.8464329547. The cubic root of 21556023 is about 278.3061986846.

The spelling of 21556023 in words is "twenty-one million, five hundred fifty-six thousand, twenty-three".