667994561 has 8 divisors (see below), whose sum is σ = 722791104. Its totient is φ = 613685520.

The previous prime is 667994557. The next prime is 667994581. The reversal of 667994561 is 165499766.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 667994561 - 2² = 667994557 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (667994501) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 119021 + ... + 124506.

It is an arithmetic number, because the mean of its divisors is an integer number (90348888).

Almost surely, 2^667994561 is an apocalyptic number.

It is an amenable number.

667994561 is a deficient number, since it is larger than the sum of its proper divisors (54796543).

667994561 is a wasteful number, since it uses less digits than its factorization.

667994561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 243751.

The product of its digits is 2449440, while the sum is 53.

The square root of 667994561 is about 25845.5907458119. The cubic root of 667994561 is about 874.1600913394.

The spelling of 667994561 in words is "six hundred sixty-seven million, nine hundred ninety-four thousand, five hundred sixty-one".