19897664 has 14 divisors (see below), whose sum is σ = 39484554. Its totient is φ = 9948800.

The previous prime is 19897663. The next prime is 19897699. The reversal of 19897664 is 46679891.

It can be written as a sum of positive squares in only one way, i.e., 17707264 + 2190400 = 4208^2 + 1480^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19897663) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 155387 + ... + 155514.

Almost surely, 2^19897664 is an apocalyptic number.

It is an amenable number.

19897664 is a deficient number, since it is larger than the sum of its proper divisors (19586890).

19897664 is an equidigital number, since it uses as much as digits as its factorization.

19897664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 310913 (or 310903 counting only the distinct ones).

The product of its digits is 653184, while the sum is 50.

The square root of 19897664 is about 4460.6797688245. The cubic root of 19897664 is about 270.9779986950.

The spelling of 19897664 in words is "nineteen million, eight hundred ninety-seven thousand, six hundred sixty-four".