209761664 has 64 divisors (see below), whose sum is σ = 480452640. Its totient is φ = 89358336.

The previous prime is 209761661. The next prime is 209761681. The reversal of 209761664 is 466167902.

It is a tau number, because it is divible by the number of its divisors (64).

It is a Smith number, since the sum of its digits (41) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (209761661) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 172322 + ... + 173534.

Almost surely, 2^209761664 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 209761664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (240226320).

209761664 is an abundant number, since it is smaller than the sum of its proper divisors (270690976).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

209761664 is a wasteful number, since it uses less digits than its factorization.

209761664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1427 (or 1415 counting only the distinct ones).

The product of its (nonzero) digits is 108864, while the sum is 41.

The square root of 209761664 is about 14483.1510383618. The cubic root of 209761664 is about 594.1672449818.

The spelling of 209761664 in words is "two hundred nine million, seven hundred sixty-one thousand, six hundred sixty-four".