66978251 has 8 divisors (see below), whose sum is σ = 69473424. Its totient is φ = 64519200.

The previous prime is 66978217. The next prime is 66978269. The reversal of 66978251 is 15287966.

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

It is a cyclic number.

It is not a de Polignac number, because 66978251 - 2⁶ = 66978187 is a prime.

It is a super-2 number, since 2×66978251² = 8972172214038002, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66978451) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5225 + ... + 12698.

It is an arithmetic number, because the mean of its divisors is an integer number (8684178).

Almost surely, 2^66978251 is an apocalyptic number.

66978251 is a deficient number, since it is larger than the sum of its proper divisors (2495173).

66978251 is a wasteful number, since it uses less digits than its factorization.

66978251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18061.

The product of its digits is 181440, while the sum is 44.

The square root of 66978251 is about 8184.0241324180. The cubic root of 66978251 is about 406.1108577214.

It can be divided in two parts, 66 and 978251, that multiplied together give a triangular number (64564566 = T₁₁₃₆₃).

The spelling of 66978251 in words is "sixty-six million, nine hundred seventy-eight thousand, two hundred fifty-one".