661679720 has 32 divisors (see below), whose sum is σ = 1603302120. Its totient is φ = 244312320.

The previous prime is 661679713. The next prime is 661679737. The reversal of 661679720 is 27976166.

661679720 is digitally balanced in base 2 and base 6, because in such bases it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 502566724 + 159112996 = 22418^2 + 12614^2 .

It is a super-3 number, since 3×661679720³ (a number of 27 digits) contains 333 as substring.

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, 635711 + ... + 636750.

Almost surely, 2^661679720 is an apocalyptic number.

It is an amenable number.

661679720 is an abundant number, since it is smaller than the sum of its proper divisors (941622400).

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

661679720 is a wasteful number, since it uses less digits than its factorization.

661679720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1272485 (or 1272481 counting only the distinct ones).

The product of its (nonzero) digits is 190512, while the sum is 44.

The square root of 661679720 is about 25723.1358897005. The cubic root of 661679720 is about 871.3967610507.

The spelling of 661679720 in words is "six hundred sixty-one million, six hundred seventy-nine thousand, seven hundred twenty".