661536724 has 12 divisors (see below), whose sum is σ = 1158843700. Its totient is φ = 330438528.

The previous prime is 661536721. The next prime is 661536751. The reversal of 661536724 is 427635166.

It can be written as a sum of positive squares in 2 ways, for example, as 282845124 + 378691600 = 16818^2 + 19460^2 .

It is a hoax number, since the sum of its digits (40) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661536721) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 77919 + ... + 85990.

Almost surely, 2^661536724 is an apocalyptic number.

It is an amenable number.

661536724 is a deficient number, since it is larger than the sum of its proper divisors (497306976).

661536724 is a wasteful number, since it uses less digits than its factorization.

661536724 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 164922 (or 164920 counting only the distinct ones).

The product of its digits is 181440, while the sum is 40.

The square root of 661536724 is about 25720.3562183730. The cubic root of 661536724 is about 871.3339838365. Note that the first 3 decimals are identical.

The spelling of 661536724 in words is "six hundred sixty-one million, five hundred thirty-six thousand, seven hundred twenty-four".