21664895 has 8 divisors (see below), whose sum is σ = 29711904. Its totient is φ = 14855904.

The previous prime is 21664891. The next prime is 21664897. The reversal of 21664895 is 59846612.

It is a happy number.

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

It is not a de Polignac number, because 21664895 - 2² = 21664891 is a prime.

It is a super-2 number, since 2×21664895² = 938735350722050, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21664891) 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, 309464 + ... + 309533.

It is an arithmetic number, because the mean of its divisors is an integer number (3713988).

Almost surely, 2^21664895 is an apocalyptic number.

21664895 is a deficient number, since it is larger than the sum of its proper divisors (8047009).

21664895 is an equidigital number, since it uses as much as digits as its factorization.

21664895 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 619009.

The product of its digits is 103680, while the sum is 41.

The square root of 21664895 is about 4654.5563698381. The cubic root of 21664895 is about 278.7739547875.

The spelling of 21664895 in words is "twenty-one million, six hundred sixty-four thousand, eight hundred ninety-five".