667728578 has 36 divisors (see below), whose sum is σ = 1115920806. Its totient is φ = 299428800.

The previous prime is 667728569. The next prime is 667728599. The reversal of 667728578 is 875827766.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 500103769 + 167624809 = 22363^2 + 12947^2 .

It is a super-2 number, since 2×667728578² = 891722907755804168, which contains 22 as substring.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 2770538 + ... + 2770778.

Almost surely, 2^667728578 is an apocalyptic number.

667728578 is a deficient number, since it is larger than the sum of its proper divisors (448192228).

667728578 is a wasteful number, since it uses less digits than its factorization.

667728578 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 479 (or 361 counting only the distinct ones).

The product of its digits is 7902720, while the sum is 56.

The square root of 667728578 is about 25840.4446169179. Note that the first 3 decimals coincide. The cubic root of 667728578 is about 874.0440511776.

The spelling of 667728578 in words is "six hundred sixty-seven million, seven hundred twenty-eight thousand, five hundred seventy-eight".