21756897 has 8 divisors (see below), whose sum is σ = 32232480. Its totient is φ = 14504580.

The previous prime is 21756883. The next prime is 21756901. The reversal of 21756897 is 79865712.

It is not a de Polignac number, because 21756897 - 2⁷ = 21756769 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21756857) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 402879 + ... + 402932.

It is an arithmetic number, because the mean of its divisors is an integer number (4029060).

Almost surely, 2^21756897 is an apocalyptic number.

21756897 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21756897 is a deficient number, since it is larger than the sum of its proper divisors (10475583).

21756897 is an equidigital number, since it uses as much as digits as its factorization.

21756897 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 805820 (or 805814 counting only the distinct ones).

The product of its digits is 211680, while the sum is 45.

The square root of 21756897 is about 4664.4289039495. The cubic root of 21756897 is about 279.1680107259.

The spelling of 21756897 in words is "twenty-one million, seven hundred fifty-six thousand, eight hundred ninety-seven".