21378904 has 8 divisors (see below), whose sum is σ = 40085460. Its totient is φ = 10689448.

The previous prime is 21378899. The next prime is 21378923. The reversal of 21378904 is 40987312.

It is a tau number, because it is divible by the number of its divisors (8).

It is a self number, because there is not a number n which added to its sum of digits gives 21378904.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1336174 + ... + 1336189.

Almost surely, 2^21378904 is an apocalyptic number.

It is an amenable number.

21378904 is a deficient number, since it is larger than the sum of its proper divisors (18706556).

21378904 is a wasteful number, since it uses less digits than its factorization.

21378904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2672369 (or 2672365 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 34.

The square root of 21378904 is about 4623.7326912355. The cubic root of 21378904 is about 277.5418501393.

The spelling of 21378904 in words is "twenty-one million, three hundred seventy-eight thousand, nine hundred four".