66628981 has 8 divisors (see below), whose sum is σ = 67579200. Its totient is φ = 65685312.

The previous prime is 66628943. The next prime is 66628987. The reversal of 66628981 is 18982666.

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 66628981 - 2⁷ = 66628853 is a prime.

It is a super-2 number, since 2×66628981² = 8878842218196722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66628987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 21006 + ... + 23968.

It is an arithmetic number, because the mean of its divisors is an integer number (8447400).

Almost surely, 2^66628981 is an apocalyptic number.

It is an amenable number.

66628981 is a deficient number, since it is larger than the sum of its proper divisors (950219).

66628981 is a wasteful number, since it uses less digits than its factorization.

66628981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3275.

The product of its digits is 248832, while the sum is 46.

The square root of 66628981 is about 8162.6577166999. The cubic root of 66628981 is about 405.4037146914.

The spelling of 66628981 in words is "sixty-six million, six hundred twenty-eight thousand, nine hundred eighty-one".