66993961 has 4 divisors (see below), whose sum is σ = 68258052. Its totient is φ = 65729872.

The previous prime is 66993937. The next prime is 66994003. The reversal of 66993961 is 16939966.

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

It can be written as a sum of positive squares in 2 ways, for example, as 58905625 + 8088336 = 7675^2 + 2844^2 .

It is a cyclic number.

It is not a de Polignac number, because 66993961 - 2⁵ = 66993929 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66993911) 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, 631966 + ... + 632071.

It is an arithmetic number, because the mean of its divisors is an integer number (17064513).

Almost surely, 2^66993961 is an apocalyptic number.

It is an amenable number.

66993961 is a deficient number, since it is larger than the sum of its proper divisors (1264091).

66993961 is a wasteful number, since it uses less digits than its factorization.

66993961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1264090.

The product of its digits is 472392, while the sum is 49.

The square root of 66993961 is about 8184.9838729224. The cubic root of 66993961 is about 406.1426068476.

The spelling of 66993961 in words is "sixty-six million, nine hundred ninety-three thousand, nine hundred sixty-one".