21811995 has 24 divisors (see below), whose sum is σ = 38615616. Its totient is φ = 11384448.

The previous prime is 21811987. The next prime is 21812017. The reversal of 21811995 is 59911812.

It is not a de Polignac number, because 21811995 - 2³ = 21811987 is a prime.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3042 + ... + 7271.

It is an arithmetic number, because the mean of its divisors is an integer number (1608984).

Almost surely, 2^21811995 is an apocalyptic number.

21811995 is a deficient number, since it is larger than the sum of its proper divisors (16803621).

21811995 is a wasteful number, since it uses less digits than its factorization.

21811995 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10371 (or 10368 counting only the distinct ones).

The product of its digits is 6480, while the sum is 36.

The square root of 21811995 is about 4670.3313586939. The cubic root of 21811995 is about 279.4034706658.

The spelling of 21811995 in words is "twenty-one million, eight hundred eleven thousand, nine hundred ninety-five".