66149981 has 4 divisors (see below), whose sum is σ = 66178464. Its totient is φ = 66121500.

The previous prime is 66149947. The next prime is 66149983. The reversal of 66149981 is 18994166.

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, and also an emirpimes, since its reverse is a distinct semiprime: 18994166 = 2 ⋅9497083.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66149981 is a prime.

It is a super-2 number, since 2×66149981² = 8751639972600722, 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 (66149983) 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, 10415 + ... + 15516.

It is an arithmetic number, because the mean of its divisors is an integer number (16544616).

Almost surely, 2^66149981 is an apocalyptic number.

It is an amenable number.

66149981 is a deficient number, since it is larger than the sum of its proper divisors (28483).

66149981 is a wasteful number, since it uses less digits than its factorization.

66149981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28482.

The product of its digits is 93312, while the sum is 44.

The square root of 66149981 is about 8133.2638589929. The cubic root of 66149981 is about 404.4298862454.

The spelling of 66149981 in words is "sixty-six million, one hundred forty-nine thousand, nine hundred eighty-one".