661209984 has 48 divisors (see below), whose sum is σ = 1902703920. Its totient is φ = 220402944.

The previous prime is 661209961. The next prime is 661210009. The reversal of 661209984 is 489902166.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (48).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 285832 + ... + 288135.

It is an arithmetic number, because the mean of its divisors is an integer number (39639665).

Almost surely, 2^661209984 is an apocalyptic number.

661209984 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

661209984 is an abundant number, since it is smaller than the sum of its proper divisors (1241493936).

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

661209984 is a wasteful number, since it uses less digits than its factorization.

661209984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 573987 (or 573972 counting only the distinct ones).

The product of its (nonzero) digits is 186624, while the sum is 45.

The square root of 661209984 is about 25714.0036555959. The cubic root of 661209984 is about 871.1905065155.

The spelling of 661209984 in words is "six hundred sixty-one million, two hundred nine thousand, nine hundred eighty-four".