21693581 has 32 divisors (see below), whose sum is σ = 29111040. Its totient is φ = 15676416.

The previous prime is 21693571. The next prime is 21693599. The reversal of 21693581 is 18539612.

It is not a de Polignac number, because 21693581 - 2¹⁰ = 21692557 is a prime.

It is a super-2 number, since 2×21693581² = 941222913207122, which contains 22 as substring.

It is a plaindrome in base 11.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21693571) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 57050 + ... + 57428.

It is an arithmetic number, because the mean of its divisors is an integer number (909720).

Almost surely, 2^21693581 is an apocalyptic number.

It is an amenable number.

21693581 is a deficient number, since it is larger than the sum of its proper divisors (7417459).

21693581 is a wasteful number, since it uses less digits than its factorization.

21693581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 453.

The product of its digits is 12960, while the sum is 35.

The square root of 21693581 is about 4657.6368471576. The cubic root of 21693581 is about 278.8969399631.

The spelling of 21693581 in words is "twenty-one million, six hundred ninety-three thousand, five hundred eighty-one".