661691582 has 4 divisors (see below), whose sum is σ = 992537376. Its totient is φ = 330845790.

The previous prime is 661691573. The next prime is 661691599. The reversal of 661691582 is 285196166.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 285196166 = 2 ⋅142598083.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 165422894 + ... + 165422897.

It is an arithmetic number, because the mean of its divisors is an integer number (248134344).

Almost surely, 2^661691582 is an apocalyptic number.

661691582 is a deficient number, since it is larger than the sum of its proper divisors (330845794).

661691582 is a wasteful number, since it uses less digits than its factorization.

661691582 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 330845793.

The product of its digits is 155520, while the sum is 44.

The square root of 661691582 is about 25723.3664593109. The cubic root of 661691582 is about 871.4019682259.

The spelling of 661691582 in words is "six hundred sixty-one million, six hundred ninety-one thousand, five hundred eighty-two".