21755643 has 16 divisors (see below), whose sum is σ = 35702016. Its totient is φ = 11475360.

The previous prime is 21755633. The next prime is 21755651. The reversal of 21755643 is 34655712.

It is not a de Polignac number, because 21755643 - 2⁵ = 21755611 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21755633) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 39573 + ... + 40118.

It is an arithmetic number, because the mean of its divisors is an integer number (2231376).

Almost surely, 2^21755643 is an apocalyptic number.

21755643 is a deficient number, since it is larger than the sum of its proper divisors (13946373).

21755643 is a wasteful number, since it uses less digits than its factorization.

21755643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79714.

The product of its digits is 25200, while the sum is 33.

The square root of 21755643 is about 4664.2944804118. The cubic root of 21755643 is about 279.1626471637.

The spelling of 21755643 in words is "twenty-one million, seven hundred fifty-five thousand, six hundred forty-three".