21641904 has 50 divisors (see below), whose sum is σ = 62641700. Its totient is φ = 7213536.

The previous prime is 21641903. The next prime is 21641909. The reversal of 21641904 is 40914612.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21641903) 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 9 ways as a sum of consecutive naturals, for example, 7054 + ... + 9645.

It is an arithmetic number, because the mean of its divisors is an integer number (1252834).

Almost surely, 2^21641904 is an apocalyptic number.

21641904 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21641904 is an abundant number, since it is smaller than the sum of its proper divisors (40999796).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21641904 is a wasteful number, since it uses less digits than its factorization.

21641904 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16719 (or 16704 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 21641904 is about 4652.0859837282. The cubic root of 21641904 is about 278.6753073283.

The spelling of 21641904 in words is "twenty-one million, six hundred forty-one thousand, nine hundred four".