66401993 has 4 divisors (see below), whose sum is σ = 75888000. Its totient is φ = 56915988.

The previous prime is 66401957. The next prime is 66402043. The reversal of 66401993 is 39910466.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 66401993 - 2²² = 62207689 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (66401593) 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, 4742993 + ... + 4743006.

It is an arithmetic number, because the mean of its divisors is an integer number (18972000).

Almost surely, 2^66401993 is an apocalyptic number.

It is an amenable number.

66401993 is a deficient number, since it is larger than the sum of its proper divisors (9486007).

66401993 is an equidigital number, since it uses as much as digits as its factorization.

66401993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9486006.

The product of its (nonzero) digits is 34992, while the sum is 38.

The square root of 66401993 is about 8148.7418047205. The cubic root of 66401993 is about 404.9428217811.

The spelling of 66401993 in words is "sixty-six million, four hundred one thousand, nine hundred ninety-three".