21901605 has 32 divisors (see below), whose sum is σ = 38579328. Its totient is φ = 10609280.

The previous prime is 21901603. The next prime is 21901613. The reversal of 21901605 is 50610912.

It is not a de Polignac number, because 21901605 - 2¹ = 21901603 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21901601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 19417 + ... + 20513.

It is an arithmetic number, because the mean of its divisors is an integer number (1205604).

Almost surely, 2^21901605 is an apocalyptic number.

It is an amenable number.

21901605 is a deficient number, since it is larger than the sum of its proper divisors (16677723).

21901605 is a wasteful number, since it uses less digits than its factorization.

21901605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1138 (or 1116 counting only the distinct ones).

The product of its (nonzero) digits is 540, while the sum is 24.

The square root of 21901605 is about 4679.9150633318. The cubic root of 21901605 is about 279.7855713732.

The spelling of 21901605 in words is "twenty-one million, nine hundred one thousand, six hundred five".