661651560 has 192 divisors, whose sum is σ = 2309608080. Its totient is φ = 163676160.

The previous prime is 661651531. The next prime is 661651583. The reversal of 661651560 is 65156166.

It can be written as a sum of positive squares in 8 ways, for example, as 380016036 + 281635524 = 19494^2 + 16782^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 446020 + ... + 447500.

Almost surely, 2^661651560 is an apocalyptic number.

661651560 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661651560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1154804040).

661651560 is an abundant number, since it is smaller than the sum of its proper divisors (1647956520).

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

661651560 is a wasteful number, since it uses less digits than its factorization.

661651560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1588 (or 1581 counting only the distinct ones).

The product of its (nonzero) digits is 32400, while the sum is 36.

The square root of 661651560 is about 25722.5885167104. The cubic root of 661651560 is about 871.3843991380.

The spelling of 661651560 in words is "six hundred sixty-one million, six hundred fifty-one thousand, five hundred sixty".