66349981 has 4 divisors (see below), whose sum is σ = 66373600. Its totient is φ = 66326364.

The previous prime is 66349979. The next prime is 66350003. The reversal of 66349981 is 18994366.

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 66349981 - 2¹ = 66349979 is a prime.

It is a super-2 number, since 2×66349981² = 8804639957400722, 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 (66349961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6921 + ... + 13438.

It is an arithmetic number, because the mean of its divisors is an integer number (16593400).

Almost surely, 2^66349981 is an apocalyptic number.

It is an amenable number.

66349981 is a deficient number, since it is larger than the sum of its proper divisors (23619).

66349981 is a wasteful number, since it uses less digits than its factorization.

66349981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23618.

The product of its digits is 279936, while the sum is 46.

The square root of 66349981 is about 8145.5497665903. The cubic root of 66349981 is about 404.8370649773.

The spelling of 66349981 in words is "sixty-six million, three hundred forty-nine thousand, nine hundred eighty-one".