661665215020 has 96 divisors (see below), whose sum is σ = 1449438484032. Its totient is φ = 253493280768.

The previous prime is 661665215011. The next prime is 661665215039. The reversal of 661665215020 is 20512566166.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 125479104 + ... + 125484376.

It is an arithmetic number, because the mean of its divisors is an integer number (15098317542).

Almost surely, 2^661665215020 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 661665215020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (724719242016).

661665215020 is an abundant number, since it is smaller than the sum of its proper divisors (787773269012).

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

661665215020 is a wasteful number, since it uses less digits than its factorization.

661665215020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8131 (or 8129 counting only the distinct ones).

The product of its (nonzero) digits is 129600, while the sum is 40.

The spelling of 661665215020 in words is "six hundred sixty-one billion, six hundred sixty-five million, two hundred fifteen thousand, twenty".