21701565 has 24 divisors (see below), whose sum is σ = 37773528. Its totient is φ = 11525760.

The previous prime is 21701551. The next prime is 21701609. The reversal of 21701565 is 56510712.

It can be written as a sum of positive squares in 4 ways, for example, as 1153476 + 20548089 = 1074^2 + 4533^2 .

It is not a de Polignac number, because 21701565 - 2¹⁸ = 21439421 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 11595 + ... + 13335.

It is an arithmetic number, because the mean of its divisors is an integer number (1573897).

Almost surely, 2^21701565 is an apocalyptic number.

It is an amenable number.

21701565 is a deficient number, since it is larger than the sum of its proper divisors (16071963).

21701565 is a wasteful number, since it uses less digits than its factorization.

21701565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2029 (or 2026 counting only the distinct ones).

The product of its (nonzero) digits is 2100, while the sum is 27.

The square root of 21701565 is about 4658.4938553142. The cubic root of 21701565 is about 278.9311503908.

The spelling of 21701565 in words is "twenty-one million, seven hundred one thousand, five hundred sixty-five".