661645594 has 4 divisors (see below), whose sum is σ = 992468394. Its totient is φ = 330822796.

The previous prime is 661645573. The next prime is 661645597. The reversal of 661645594 is 495546166.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 610337025 + 51308569 = 24705^2 + 7163^2 .

It is a super-2 number, since 2×661645594² = 875549784119225672, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (661645597) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 165411397 + ... + 165411400.

Almost surely, 2^661645594 is an apocalyptic number.

661645594 is a deficient number, since it is larger than the sum of its proper divisors (330822800).

661645594 is a wasteful number, since it uses less digits than its factorization.

661645594 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 330822799.

The product of its digits is 777600, while the sum is 46.

The square root of 661645594 is about 25722.4725483380. The cubic root of 661645594 is about 871.3817800883.

The spelling of 661645594 in words is "six hundred sixty-one million, six hundred forty-five thousand, five hundred ninety-four".