21566983 has 4 divisors (see below), whose sum is σ = 21621168. Its totient is φ = 21512800.

The previous prime is 21566971. The next prime is 21567011. The reversal of 21566983 is 38966512.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21566983 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 (21566953) 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, 26491 + ... + 27292.

It is an arithmetic number, because the mean of its divisors is an integer number (5405292).

Almost surely, 2^21566983 is an apocalyptic number.

21566983 is a deficient number, since it is larger than the sum of its proper divisors (54185).

21566983 is an equidigital number, since it uses as much as digits as its factorization.

21566983 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 54184.

The product of its digits is 77760, while the sum is 40.

The square root of 21566983 is about 4644.0265933778. The cubic root of 21566983 is about 278.3533582670.

The spelling of 21566983 in words is "twenty-one million, five hundred sixty-six thousand, nine hundred eighty-three".