66978738 has 30 divisors (see below), whose sum is σ = 150315759. Its totient is φ = 22291524.

The previous prime is 66978727. The next prime is 66978739. The reversal of 66978738 is 83787966.

It can be written as a sum of positive squares in only one way, i.e., 33489369 + 33489369 = 5787^2 + 5787^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=5787.

It is a Harshad number since it is a multiple of its sum of digits (54).

Its product of digits (3048192) is a multiple of the sum of its prime divisors (648).

It is not an unprimeable number, because it can be changed into a prime (66978739) by changing a digit.

It is a polite number, since it can be written in 14 ways as a sum of consecutive naturals, for example, 103845 + ... + 104487.

Almost surely, 2^66978738 is an apocalyptic number.

66978738 is an abundant number, since it is smaller than the sum of its proper divisors (83337021).

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

66978738 is an frugal number, since it uses more digits than its factorization.

66978738 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1300 (or 648 counting only the distinct ones).

The product of its digits is 3048192, while the sum is 54.

The square root of 66978738 is about 8184.0538854531. The cubic root of 66978738 is about 406.1118419987. Note that the first 3 decimals are identical.

The spelling of 66978738 in words is "sixty-six million, nine hundred seventy-eight thousand, seven hundred thirty-eight".