66939778 has 8 divisors (see below), whose sum is σ = 106316172. Its totient is φ = 31501056.

The previous prime is 66939739. The next prime is 66939787. The reversal of 66939778 is 87793966.

It can be written as a sum of positive squares in 2 ways, for example, as 57957769 + 8982009 = 7613^2 + 2997^2 .

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, 984375 + ... + 984442.

Almost surely, 2^66939778 is an apocalyptic number.

66939778 is a deficient number, since it is larger than the sum of its proper divisors (39376394).

66939778 is a wasteful number, since it uses less digits than its factorization.

66939778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1968836.

The product of its digits is 3429216, while the sum is 55.

The square root of 66939778 is about 8181.6733007374. The cubic root of 66939778 is about 406.0330847362.

It can be divided in two parts, 6693 and 9778, that added together give a triangular number (16471 = T₁₈₁).

The spelling of 66939778 in words is "sixty-six million, nine hundred thirty-nine thousand, seven hundred seventy-eight".