66998981 has 4 divisors (see below), whose sum is σ = 76570272. Its totient is φ = 57427692.

The previous prime is 66998947. The next prime is 66998983. The reversal of 66998981 is 18989966.

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 de Polignac number, because none of the positive numbers 2^k-66998981 is a prime.

It is a super-2 number, since 2×66998981² = 8977726910076722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66998983) 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, 4785635 + ... + 4785648.

It is an arithmetic number, because the mean of its divisors is an integer number (19142568).

Almost surely, 2^66998981 is an apocalyptic number.

It is an amenable number.

66998981 is a deficient number, since it is larger than the sum of its proper divisors (9571291).

66998981 is an equidigital number, since it uses as much as digits as its factorization.

66998981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9571290.

The product of its digits is 1679616, while the sum is 56.

The square root of 66998981 is about 8185.2905263039. The cubic root of 66998981 is about 406.1527509707.

The spelling of 66998981 in words is "sixty-six million, nine hundred ninety-eight thousand, nine hundred eighty-one".