66402991 has 2 divisors, whose sum is σ = 66402992. Its totient is φ = 66402990.

The previous prime is 66402979. The next prime is 66403009. The reversal of 66402991 is 19920466.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 66402991 - 2¹⁵ = 66370223 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 66402991.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66402911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33201495 + 33201496.

It is an arithmetic number, because the mean of its divisors is an integer number (33201496).

Almost surely, 2^66402991 is an apocalyptic number.

66402991 is a deficient number, since it is larger than the sum of its proper divisors (1).

66402991 is an equidigital number, since it uses as much as digits as its factorization.

66402991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 23328, while the sum is 37.

The square root of 66402991 is about 8148.8030409380. The cubic root of 66402991 is about 404.9448504898.

The spelling of 66402991 in words is "sixty-six million, four hundred two thousand, nine hundred ninety-one".