661377317020 has 192 divisors, whose sum is σ = 1745888981760. Its totient is φ = 205199769600.

The previous prime is 661377316973. The next prime is 661377317021. The reversal of 661377317020 is 20713773166.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661377317021) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 16613940 + ... + 16653700.

It is an arithmetic number, because the mean of its divisors is an integer number (9093171780).

Almost surely, 2^661377317020 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661377317020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (872944490880).

661377317020 is an abundant number, since it is smaller than the sum of its proper divisors (1084511664740).

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

661377317020 is a wasteful number, since it uses less digits than its factorization.

661377317020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40064 (or 40062 counting only the distinct ones).

The product of its (nonzero) digits is 222264, while the sum is 43.

The spelling of 661377317020 in words is "six hundred sixty-one billion, three hundred seventy-seven million, three hundred seventeen thousand, twenty".