66639780 has 48 divisors (see below), whose sum is σ = 207325440. Its totient is φ = 17770464.

The previous prime is 66639751. The next prime is 66639791. The reversal of 66639780 is 8793666.

It is a Harshad number since it is a multiple of its sum of digits (45).

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, 61164 + ... + 62243.

It is an arithmetic number, because the mean of its divisors is an integer number (4319280).

Almost surely, 2^66639780 is an apocalyptic number.

66639780 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

66639780 is an abundant number, since it is smaller than the sum of its proper divisors (140685660).

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

66639780 is a wasteful number, since it uses less digits than its factorization.

66639780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 123425 (or 123417 counting only the distinct ones).

The product of its (nonzero) digits is 326592, while the sum is 45.

The square root of 66639780 is about 8163.3191778835. The cubic root of 66639780 is about 405.4256156627.

The spelling of 66639780 in words is "sixty-six million, six hundred thirty-nine thousand, seven hundred eighty".