66639994 has 8 divisors (see below), whose sum is σ = 100083060. Its totient is φ = 33278976.

The previous prime is 66639977. The next prime is 66640003. The reversal of 66639994 is 49993666.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 65853225 + 786769 = 8115^2 + 887^2 .

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

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18439 + ... + 21754.

Almost surely, 2^66639994 is an apocalyptic number.

66639994 is a deficient number, since it is larger than the sum of its proper divisors (33443066).

66639994 is a wasteful number, since it uses less digits than its factorization.

66639994 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41024.

The product of its digits is 1889568, while the sum is 52.

The square root of 66639994 is about 8163.3322852864. The cubic root of 66639994 is about 405.4260496427.

The spelling of 66639994 in words is "sixty-six million, six hundred thirty-nine thousand, nine hundred ninety-four".