661837701980 has 288 divisors, whose sum is σ = 1800073497600. Its totient is φ = 199762827264.

The previous prime is 661837701979. The next prime is 661837702013. The reversal of 661837701980 is 89107738166.

It is a hoax number, since the sum of its digits (56) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 206242616 + ... + 206245824.

It is an arithmetic number, because the mean of its divisors is an integer number (6250255200).

Almost surely, 2^661837701980 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 661837701980, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (900036748800).

661837701980 is an abundant number, since it is smaller than the sum of its proper divisors (1138235795620).

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

661837701980 is a wasteful number, since it uses less digits than its factorization.

661837701980 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3653 (or 3638 counting only the distinct ones).

The product of its (nonzero) digits is 3048192, while the sum is 56.

The spelling of 661837701980 in words is "six hundred sixty-one billion, eight hundred thirty-seven million, seven hundred one thousand, nine hundred eighty".