66721091 has 8 divisors (see below), whose sum is σ = 69916704. Its totient is φ = 63550080.

The previous prime is 66721087. The next prime is 66721097. The reversal of 66721091 is 19012766.

It is a happy number.

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 66721091 - 2² = 66721087 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66721097) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 476 + ... + 11561.

It is an arithmetic number, because the mean of its divisors is an integer number (8739588).

Almost surely, 2^66721091 is an apocalyptic number.

66721091 is a deficient number, since it is larger than the sum of its proper divisors (3195613).

66721091 is a wasteful number, since it uses less digits than its factorization.

66721091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12301.

The product of its (nonzero) digits is 4536, while the sum is 32.

The square root of 66721091 is about 8168.2979255167. The cubic root of 66721091 is about 405.5904429556.

The spelling of 66721091 in words is "sixty-six million, seven hundred twenty-one thousand, ninety-one".