21929904 has 60 divisors (see below), whose sum is σ = 62316696. Its totient is φ = 7197696.

The previous prime is 21929903. The next prime is 21929909. The reversal of 21929904 is 40992912.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (21929903) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 8512 + ... + 10784.

Almost surely, 2^21929904 is an apocalyptic number.

21929904 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21929904, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31158348).

21929904 is an abundant number, since it is smaller than the sum of its proper divisors (40386792).

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

21929904 is a wasteful number, since it uses less digits than its factorization.

21929904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2354 (or 2345 counting only the distinct ones).

The product of its (nonzero) digits is 11664, while the sum is 36.

The square root of 21929904 is about 4682.9375396219. The cubic root of 21929904 is about 279.9060228835.

The spelling of 21929904 in words is "twenty-one million, nine hundred twenty-nine thousand, nine hundred four".