66221861 has 2 divisors, whose sum is σ = 66221862. Its totient is φ = 66221860.

The previous prime is 66221789. The next prime is 66221867. The reversal of 66221861 is 16812266.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 58828900 + 7392961 = 7670^2 + 2719^2 .

It is a cyclic number.

It is not a de Polignac number, because 66221861 - 2²² = 62027557 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66221867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33110930 + 33110931.

It is an arithmetic number, because the mean of its divisors is an integer number (33110931).

Almost surely, 2^66221861 is an apocalyptic number.

It is an amenable number.

66221861 is a deficient number, since it is larger than the sum of its proper divisors (1).

66221861 is an equidigital number, since it uses as much as digits as its factorization.

66221861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6912, while the sum is 32.

The square root of 66221861 is about 8137.6815494341. The cubic root of 66221861 is about 404.5763206390.

The spelling of 66221861 in words is "sixty-six million, two hundred twenty-one thousand, eight hundred sixty-one".