21640597 has 8 divisors (see below), whose sum is σ = 24246432. Its totient is φ = 19141200.

The previous prime is 21640561. The next prime is 21640607. The reversal of 21640597 is 79504612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21640597 - 2⁷ = 21640469 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21640537) 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, 26179 + ... + 26992.

It is an arithmetic number, because the mean of its divisors is an integer number (3030804).

Almost surely, 2^21640597 is an apocalyptic number.

It is an amenable number.

21640597 is a deficient number, since it is larger than the sum of its proper divisors (2605835).

21640597 is a wasteful number, since it uses less digits than its factorization.

21640597 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53219.

The product of its (nonzero) digits is 15120, while the sum is 34.

The square root of 21640597 is about 4651.9455069895. The cubic root of 21640597 is about 278.6696972865.

The spelling of 21640597 in words is "twenty-one million, six hundred forty thousand, five hundred ninety-seven".