661699680 has 48 divisors (see below), whose sum is σ = 2084355504. Its totient is φ = 176453120.

The previous prime is 661699679. The next prime is 661699711. The reversal of 661699680 is 86996166.

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 7 ways as a sum of consecutive naturals, for example, 688791 + ... + 689750.

It is an arithmetic number, because the mean of its divisors is an integer number (43424073).

Almost surely, 2^661699680 is an apocalyptic number.

661699680 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

661699680 is an abundant number, since it is smaller than the sum of its proper divisors (1422655824).

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

661699680 is a wasteful number, since it uses less digits than its factorization.

661699680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1378559 (or 1378551 counting only the distinct ones).

The product of its (nonzero) digits is 839808, while the sum is 51.

The square root of 661699680 is about 25723.5238643542. The cubic root of 661699680 is about 871.4055230464.

The spelling of 661699680 in words is "six hundred sixty-one million, six hundred ninety-nine thousand, six hundred eighty".