661091632440 has 64 divisors (see below), whose sum is σ = 1987217971200. Its totient is φ = 175940606592.

The previous prime is 661091632433. The next prime is 661091632451. The reversal of 661091632440 is 44236190166.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 661091632392 and 661091632401.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5415880 + ... + 5536599.

It is an arithmetic number, because the mean of its divisors is an integer number (31050280800).

Almost surely, 2^661091632440 is an apocalyptic number.

661091632440 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

661091632440 is an abundant number, since it is smaller than the sum of its proper divisors (1326126338760).

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

661091632440 is a wasteful number, since it uses less digits than its factorization.

661091632440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10952996 (or 10952992 counting only the distinct ones).

The product of its (nonzero) digits is 186624, while the sum is 42.

The spelling of 661091632440 in words is "six hundred sixty-one billion, ninety-one million, six hundred thirty-two thousand, four hundred forty".