661736694784 has 99 divisors (see below), whose sum is σ = 1454646077283. Its totient is φ = 300659251200.

The previous prime is 661736694739. The next prime is 661736694791. The reversal of 661736694784 is 487496637166.

The square root of 661736694784 is 813472.

It is a perfect power (a square), and thus also a powerful number.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 286340989 + ... + 286343299.

Almost surely, 2^661736694784 is an apocalyptic number.

661736694784 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

661736694784 is the 813472-nd square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661736694784

661736694784 is an abundant number, since it is smaller than the sum of its proper divisors (792909382499).

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

661736694784 is an frugal number, since it uses more digits than its factorization.

661736694784 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4664 (or 2324 counting only the distinct ones).

The product of its digits is 219469824, while the sum is 67.

The spelling of 661736694784 in words is "six hundred sixty-one billion, seven hundred thirty-six million, six hundred ninety-four thousand, seven hundred eighty-four".