666791558 has 4 divisors (see below), whose sum is σ = 1000187340. Its totient is φ = 333395778.

The previous prime is 666791507. The next prime is 666791599. The reversal of 666791558 is 855197666.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 855197666 = 2 ⋅427598833.

It is a super-2 number, since 2×666791558² = 889221963640134728, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 166697888 + ... + 166697891.

It is an arithmetic number, because the mean of its divisors is an integer number (250046835).

Almost surely, 2^666791558 is an apocalyptic number.

666791558 is a deficient number, since it is larger than the sum of its proper divisors (333395782).

666791558 is a wasteful number, since it uses less digits than its factorization.

666791558 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 333395781.

The product of its digits is 2721600, while the sum is 53.

The square root of 666791558 is about 25822.3073717280. The cubic root of 666791558 is about 873.6350126447.

The spelling of 666791558 in words is "six hundred sixty-six million, seven hundred ninety-one thousand, five hundred fifty-eight".