21605679 has 12 divisors (see below), whose sum is σ = 32851000. Its totient is φ = 13645584.

The previous prime is 21605677. The next prime is 21605693. The reversal of 21605679 is 97650612.

It is not a de Polignac number, because 21605679 - 2¹ = 21605677 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21605677) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 63004 + ... + 63345.

Almost surely, 2^21605679 is an apocalyptic number.

21605679 is a deficient number, since it is larger than the sum of its proper divisors (11245321).

21605679 is a wasteful number, since it uses less digits than its factorization.

21605679 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 126374 (or 126371 counting only the distinct ones).

The product of its (nonzero) digits is 22680, while the sum is 36.

The square root of 21605679 is about 4648.1909384189. The cubic root of 21605679 is about 278.5197348994.

The spelling of 21605679 in words is "twenty-one million, six hundred five thousand, six hundred seventy-nine".