19971904 has 28 divisors (see below), whose sum is σ = 39798244. Its totient is φ = 9944064.

The previous prime is 19971899. The next prime is 19971943. The reversal of 19971904 is 40917991.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 7011904 + 12960000 = 2648^2 + 3600^2 .

It is a congruent number.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 19534 + ... + 20530.

Almost surely, 2^19971904 is an apocalyptic number.

It is an amenable number.

19971904 is a deficient number, since it is larger than the sum of its proper divisors (19826340).

19971904 is an equidigital number, since it uses as much as digits as its factorization.

19971904 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1322 (or 1312 counting only the distinct ones).

The product of its (nonzero) digits is 20412, while the sum is 40.

The square root of 19971904 is about 4468.9936227298. The cubic root of 19971904 is about 271.3145949640.

The spelling of 19971904 in words is "nineteen million, nine hundred seventy-one thousand, nine hundred four".