21640911 has 8 divisors (see below), whose sum is σ = 29525760. Its totient is φ = 14091672.

The previous prime is 21640891. The next prime is 21640919. The reversal of 21640911 is 11904612.

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

It is not a de Polignac number, because 21640911 - 2⁷ = 21640783 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21640919) 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, 83751 + ... + 84008.

It is an arithmetic number, because the mean of its divisors is an integer number (3690720).

Almost surely, 2^21640911 is an apocalyptic number.

21640911 is a deficient number, since it is larger than the sum of its proper divisors (7884849).

21640911 is a wasteful number, since it uses less digits than its factorization.

21640911 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 167805.

The product of its (nonzero) digits is 432, while the sum is 24.

The square root of 21640911 is about 4651.9792561876. The cubic root of 21640911 is about 278.6710450907.

The spelling of 21640911 in words is "twenty-one million, six hundred forty thousand, nine hundred eleven".