66125981 has 4 divisors (see below), whose sum is σ = 66144252. Its totient is φ = 66107712.

The previous prime is 66125977. The next prime is 66125987. The reversal of 66125981 is 18952166.

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 15132100 + 50993881 = 3890^2 + 7141^2 .

It is a cyclic number.

It is not a de Polignac number, because 66125981 - 2² = 66125977 is a prime.

It is a super-2 number, since 2×66125981² = 8745290726424722, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66125987) 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, 1676 + ... + 11621.

It is an arithmetic number, because the mean of its divisors is an integer number (16536063).

Almost surely, 2^66125981 is an apocalyptic number.

It is an amenable number.

66125981 is a deficient number, since it is larger than the sum of its proper divisors (18271).

66125981 is a wasteful number, since it uses less digits than its factorization.

66125981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18270.

The product of its digits is 25920, while the sum is 38.

The square root of 66125981 is about 8131.7883027044. The cubic root of 66125981 is about 404.3809696712.

The spelling of 66125981 in words is "sixty-six million, one hundred twenty-five thousand, nine hundred eighty-one".