66978881 has 2 divisors, whose sum is σ = 66978882. Its totient is φ = 66978880.

The previous prime is 66978851. The next prime is 66978931. The reversal of 66978881 is 18887966.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 66569281 + 409600 = 8159^2 + 640^2 .

It is a cyclic number.

It is not a de Polignac number, because 66978881 - 2¹⁰ = 66977857 is a prime.

It is a super-2 number, since 2×66978881² = 8972341000024322, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (66978811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33489440 + 33489441.

It is an arithmetic number, because the mean of its divisors is an integer number (33489441).

Almost surely, 2^66978881 is an apocalyptic number.

It is an amenable number.

66978881 is a deficient number, since it is larger than the sum of its proper divisors (1).

66978881 is an equidigital number, since it uses as much as digits as its factorization.

66978881 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1161216, while the sum is 53.

The square root of 66978881 is about 8184.0626219501. The cubic root of 66978881 is about 406.1121310155.

The spelling of 66978881 in words is "sixty-six million, nine hundred seventy-eight thousand, eight hundred eighty-one".