21651955 has 8 divisors (see below), whose sum is σ = 27981072. Its totient is φ = 15989088.

The previous prime is 21651943. The next prime is 21651967. The reversal of 21651955 is 55915612.

It is an interprime number because it is at equal distance from previous prime (21651943) and next prime (21651967).

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21651955 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21651955.

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 7 ways as a sum of consecutive naturals, for example, 166489 + ... + 166618.

It is an arithmetic number, because the mean of its divisors is an integer number (3497634).

Almost surely, 2^21651955 is an apocalyptic number.

21651955 is a deficient number, since it is larger than the sum of its proper divisors (6329117).

21651955 is a wasteful number, since it uses less digits than its factorization.

21651955 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 333125.

The product of its digits is 13500, while the sum is 34.

The square root of 21651955 is about 4653.1661264133. The cubic root of 21651955 is about 278.7184417342.

The spelling of 21651955 in words is "twenty-one million, six hundred fifty-one thousand, nine hundred fifty-five".