21973861 has 32 divisors (see below), whose sum is σ = 29030400. Its totient is φ = 16148160.

The previous prime is 21973849. The next prime is 21973871. The reversal of 21973861 is 16837912.

It is not a de Polignac number, because 21973861 - 2⁵ = 21973829 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21973861.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21973801) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 122670 + ... + 122848.

It is an arithmetic number, because the mean of its divisors is an integer number (907200).

Almost surely, 2^21973861 is an apocalyptic number.

21973861 is the 2506-th nonagonal number.

It is an amenable number.

21973861 is a deficient number, since it is larger than the sum of its proper divisors (7056539).

21973861 is a wasteful number, since it uses less digits than its factorization.

21973861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 289.

The product of its digits is 18144, while the sum is 37.

The square root of 21973861 is about 4687.6285049052. The cubic root of 21973861 is about 280.0929155919.

The spelling of 21973861 in words is "twenty-one million, nine hundred seventy-three thousand, eight hundred sixty-one".