21947845 has 32 divisors (see below), whose sum is σ = 28892160. Its totient is φ = 15966720.

The previous prime is 21947839. The next prime is 21947851. The reversal of 21947845 is 54874912.

It is an interprime number because it is at equal distance from previous prime (21947839) and next prime (21947851).

It is not a de Polignac number, because 21947845 - 2³ = 21947837 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21947798 and 21947807.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 246561 + ... + 246649.

It is an arithmetic number, because the mean of its divisors is an integer number (902880).

Almost surely, 2^21947845 is an apocalyptic number.

It is an amenable number.

21947845 is a deficient number, since it is larger than the sum of its proper divisors (6944315).

21947845 is a wasteful number, since it uses less digits than its factorization.

21947845 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 205.

The product of its digits is 80640, while the sum is 40.

The square root of 21947845 is about 4684.8527191364. The cubic root of 21947845 is about 279.9823330690.

The spelling of 21947845 in words is "twenty-one million, nine hundred forty-seven thousand, eight hundred forty-five".