661551440 has 40 divisors (see below), whose sum is σ = 1677937248. Its totient is φ = 240563840.

The previous prime is 661551437. The next prime is 661551469. The reversal of 661551440 is 44155166.

It is a tau number, because it is divible by the number of its divisors (40).

It is a junction number, because it is equal to n+sod(n) for n = 661551397 and 661551406.

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, 375002 + ... + 376761.

Almost surely, 2^661551440 is an apocalyptic number.

It is an amenable number.

661551440 is an abundant number, since it is smaller than the sum of its proper divisors (1016385808).

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

661551440 is a wasteful number, since it uses less digits than its factorization.

661551440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 751787 (or 751781 counting only the distinct ones).

The product of its (nonzero) digits is 14400, while the sum is 32.

The square root of 661551440 is about 25720.6422936909. The cubic root of 661551440 is about 871.3404447808.

The spelling of 661551440 in words is "six hundred sixty-one million, five hundred fifty-one thousand, four hundred forty".