66889961 has 2 divisors, whose sum is σ = 66889962. Its totient is φ = 66889960.

The previous prime is 66889943. The next prime is 66889987. The reversal of 66889961 is 16998866.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 35473936 + 31416025 = 5956^2 + 5605^2 .

It is a cyclic number.

It is not a de Polignac number, because 66889961 - 2¹⁰ = 66888937 is a prime.

It is not a weakly prime, because it can be changed into another prime (66889261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33444980 + 33444981.

It is an arithmetic number, because the mean of its divisors is an integer number (33444981).

Almost surely, 2^66889961 is an apocalyptic number.

It is an amenable number.

66889961 is a deficient number, since it is larger than the sum of its proper divisors (1).

66889961 is an equidigital number, since it uses as much as digits as its factorization.

66889961 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1119744, while the sum is 53.

The square root of 66889961 is about 8178.6283079744. The cubic root of 66889961 is about 405.9323356219.

The spelling of 66889961 in words is "sixty-six million, eight hundred eighty-nine thousand, nine hundred sixty-one".