1639664978 has 16 divisors (see below), whose sum is σ = 2842439040. Its totient is φ = 694817376.

The previous prime is 1639664969. The next prime is 1639664981. The reversal of 1639664978 is 8794669361.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 656726 + ... + 659217.

It is an arithmetic number, because the mean of its divisors is an integer number (177652440).

Almost surely, 2^1639664978 is an apocalyptic number.

1639664978 is a deficient number, since it is larger than the sum of its proper divisors (1202774062).

1639664978 is a wasteful number, since it uses less digits than its factorization.

1639664978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1316041.

The product of its digits is 11757312, while the sum is 59.

The square root of 1639664978 is about 40492.7768620528. The cubic root of 1639664978 is about 1179.1934011766.

The spelling of 1639664978 in words is "one billion, six hundred thirty-nine million, six hundred sixty-four thousand, nine hundred seventy-eight".