21601657 has 8 divisors (see below), whose sum is σ = 26932032. Its totient is φ = 16832400.

The previous prime is 21601639. The next prime is 21601667. The reversal of 21601657 is 75610612.

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 21601657 - 2¹⁵ = 21568889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21601627) 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, 140194 + ... + 140347.

It is an arithmetic number, because the mean of its divisors is an integer number (3366504).

Almost surely, 2^21601657 is an apocalyptic number.

It is an amenable number.

21601657 is a deficient number, since it is larger than the sum of its proper divisors (5330375).

21601657 is a wasteful number, since it uses less digits than its factorization.

21601657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 280559.

The product of its (nonzero) digits is 2520, while the sum is 28.

The square root of 21601657 is about 4647.7582768470. The cubic root of 21601657 is about 278.5024512353.

The spelling of 21601657 in words is "twenty-one million, six hundred one thousand, six hundred fifty-seven".