661989694 has 4 divisors (see below), whose sum is σ = 992984544. Its totient is φ = 330994846.

The previous prime is 661989683. The next prime is 661989701. The reversal of 661989694 is 496989166.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 496989166 = 2 ⋅248494583.

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, 165497422 + ... + 165497425.

It is an arithmetic number, because the mean of its divisors is an integer number (248246136).

Almost surely, 2^661989694 is an apocalyptic number.

661989694 is a deficient number, since it is larger than the sum of its proper divisors (330994850).

661989694 is a wasteful number, since it uses less digits than its factorization.

661989694 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 330994849.

The product of its digits is 5038848, while the sum is 58.

The square root of 661989694 is about 25729.1603827253. The cubic root of 661989694 is about 871.5328128611.

The spelling of 661989694 in words is "six hundred sixty-one million, nine hundred eighty-nine thousand, six hundred ninety-four".