21645897 has 48 divisors (see below), whose sum is σ = 37078272. Its totient is φ = 11128320.

The previous prime is 21645881. The next prime is 21645901. The reversal of 21645897 is 79854612.

It is not a de Polignac number, because 21645897 - 2⁴ = 21645881 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21645817) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 89697 + ... + 89937.

It is an arithmetic number, because the mean of its divisors is an integer number (772464).

Almost surely, 2^21645897 is an apocalyptic number.

It is an amenable number.

21645897 is a deficient number, since it is larger than the sum of its proper divisors (15432375).

21645897 is a wasteful number, since it uses less digits than its factorization.

21645897 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 318 (or 311 counting only the distinct ones).

The product of its digits is 120960, while the sum is 42.

The square root of 21645897 is about 4652.5151262516. The cubic root of 21645897 is about 278.6924451007.

The spelling of 21645897 in words is "twenty-one million, six hundred forty-five thousand, eight hundred ninety-seven".