661440245760 has 728 divisors, whose sum is σ = 2720207509920. Its totient is φ = 151162454016.

The previous prime is 661440245743. The next prime is 661440245783. The reversal of 661440245760 is 67542044166.

661440245760 is a `hidden beast` number, since 6 + 6 + 14 + 40 + 24 + 576 + 0 = 666.

It is a super-2 number, since 2×661440245760² (a number of 24 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 55 ways as a sum of consecutive naturals, for example, 104506276 + ... + 104512604.

Almost surely, 2^661440245760 is an apocalyptic number.

661440245760 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 661440245760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1360103754960).

661440245760 is an abundant number, since it is smaller than the sum of its proper divisors (2058767264160).

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

661440245760 is an frugal number, since it uses more digits than its factorization.

661440245760 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6383 (or 6346 counting only the distinct ones).

The product of its (nonzero) digits is 967680, while the sum is 45.

The spelling of 661440245760 in words is "six hundred sixty-one billion, four hundred forty million, two hundred forty-five thousand, seven hundred sixty".