993811661 has 4 divisors (see below), whose sum is σ = 996025500. Its totient is φ = 991597824.

The previous prime is 993811633. The next prime is 993811699. The reversal of 993811661 is 166118399.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 166118399 = 1019 ⋅163021.

It can be written as a sum of positive squares in 2 ways, for example, as 711235561 + 282576100 = 26669^2 + 16810^2 .

It is a cyclic number.

It is not a de Polignac number, because 993811661 - 2⁶ = 993811597 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (993811631) 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, 1106246 + ... + 1107143.

It is an arithmetic number, because the mean of its divisors is an integer number (249006375).

Almost surely, 2^993811661 is an apocalyptic number.

It is an amenable number.

993811661 is a deficient number, since it is larger than the sum of its proper divisors (2213839).

993811661 is a wasteful number, since it uses less digits than its factorization.

993811661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2213838.

The product of its digits is 69984, while the sum is 44.

The square root of 993811661 is about 31524.7785242022. The cubic root of 993811661 is about 997.9329505840.

The spelling of 993811661 in words is "nine hundred ninety-three million, eight hundred eleven thousand, six hundred sixty-one".