19971808 has 12 divisors (see below), whose sum is σ = 39319560. Its totient is φ = 9985888.

The previous prime is 19971761. The next prime is 19971857. The reversal of 19971808 is 80817991.

It is a super-2 number, since 2×19971808² = 797746229577728, which contains 22 as substring.

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, 312028 + ... + 312091.

It is an arithmetic number, because the mean of its divisors is an integer number (3276630).

Almost surely, 2^19971808 is an apocalyptic number.

It is an amenable number.

19971808 is a deficient number, since it is larger than the sum of its proper divisors (19347752).

19971808 is an equidigital number, since it uses as much as digits as its factorization.

19971808 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 624129 (or 624121 counting only the distinct ones).

The product of its (nonzero) digits is 36288, while the sum is 43.

The square root of 19971808 is about 4468.9828820437. The cubic root of 19971808 is about 271.3141602493.

The spelling of 19971808 in words is "nineteen million, nine hundred seventy-one thousand, eight hundred eight".