21905901 has 12 divisors (see below), whose sum is σ = 32315712. Its totient is φ = 14292936.

The previous prime is 21905899. The next prime is 21905927. The reversal of 21905901 is 10950912.

It is a happy number.

It is not a de Polignac number, because 21905901 - 2¹ = 21905899 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21905501) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 25471 + ... + 26316.

It is an arithmetic number, because the mean of its divisors is an integer number (2692976).

Almost surely, 2^21905901 is an apocalyptic number.

It is an amenable number.

21905901 is a deficient number, since it is larger than the sum of its proper divisors (10409811).

21905901 is a wasteful number, since it uses less digits than its factorization.

21905901 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51840 (or 51837 counting only the distinct ones).

The product of its (nonzero) digits is 810, while the sum is 27.

The square root of 21905901 is about 4680.3740235156. The cubic root of 21905901 is about 279.8038634912.

The spelling of 21905901 in words is "twenty-one million, nine hundred five thousand, nine hundred one".