19921808 has 10 divisors (see below), whose sum is σ = 38598534. Its totient is φ = 9960896.

The previous prime is 19921801. The next prime is 19921817. The reversal of 19921808 is 80812991.

It can be written as a sum of positive squares in only one way, i.e., 17205904 + 2715904 = 4148^2 + 1648^2 .

It is not an unprimeable number, because it can be changed into a prime (19921801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 622541 + ... + 622572.

Almost surely, 2^19921808 is an apocalyptic number.

It is an amenable number.

19921808 is a deficient number, since it is larger than the sum of its proper divisors (18676726).

19921808 is a wasteful number, since it uses less digits than its factorization.

19921808 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1245121 (or 1245115 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 38.

The square root of 19921808 is about 4463.3852623317. The cubic root of 19921808 is about 271.0875567540.

The spelling of 19921808 in words is "nineteen million, nine hundred twenty-one thousand, eight hundred eight".