19911664 has 10 divisors (see below), whose sum is σ = 38578880. Its totient is φ = 9955824.

The previous prime is 19911659. The next prime is 19911673. The reversal of 19911664 is 46611991.

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, 622224 + ... + 622255.

It is an arithmetic number, because the mean of its divisors is an integer number (3857888).

Almost surely, 2^19911664 is an apocalyptic number.

It is an amenable number.

19911664 is a deficient number, since it is larger than the sum of its proper divisors (18667216).

19911664 is a wasteful number, since it uses less digits than its factorization.

19911664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1244487 (or 1244481 counting only the distinct ones).

The product of its digits is 11664, while the sum is 37.

The square root of 19911664 is about 4462.2487604346. The cubic root of 19911664 is about 271.0415371851.

It can be divided in two parts, 1991 and 1664, that added together give a triangular number (3655 = T₈₅).

The spelling of 19911664 in words is "nineteen million, nine hundred eleven thousand, six hundred sixty-four".