66615978 has 32 divisors (see below), whose sum is σ = 156526272. Its totient is φ = 18633600.

The previous prime is 66615959. The next prime is 66616031. The reversal of 66615978 is 87951666.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 37963 + ... + 39678.

It is an arithmetic number, because the mean of its divisors is an integer number (4891446).

Almost surely, 2^66615978 is an apocalyptic number.

66615978 is an abundant number, since it is smaller than the sum of its proper divisors (89910294).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

66615978 is a wasteful number, since it uses less digits than its factorization.

66615978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77670.

The product of its digits is 544320, while the sum is 48.

The square root of 66615978 is about 8161.8611848034. The cubic root of 66615978 is about 405.3773407453.

The spelling of 66615978 in words is "sixty-six million, six hundred fifteen thousand, nine hundred seventy-eight".