66891491 has 4 divisors (see below), whose sum is σ = 67581192. Its totient is φ = 66201792.

The previous prime is 66891479. The next prime is 66891499. The reversal of 66891491 is 19419866.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66891491 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66891499) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 344705 + ... + 344898.

It is an arithmetic number, because the mean of its divisors is an integer number (16895298).

Almost surely, 2^66891491 is an apocalyptic number.

66891491 is a deficient number, since it is larger than the sum of its proper divisors (689701).

66891491 is an equidigital number, since it uses as much as digits as its factorization.

66891491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 689700.

The product of its digits is 93312, while the sum is 44.

The square root of 66891491 is about 8178.7218439069. The cubic root of 66891491 is about 405.9354306142.

The spelling of 66891491 in words is "sixty-six million, eight hundred ninety-one thousand, four hundred ninety-one".