66381861 has 16 divisors (see below), whose sum is σ = 108934784. Its totient is φ = 35014464.

The previous prime is 66381857. The next prime is 66381863. The reversal of 66381861 is 16818366.

It is not a de Polignac number, because 66381861 - 2² = 66381857 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66381863) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 121306 + ... + 121851.

It is an arithmetic number, because the mean of its divisors is an integer number (6808424).

Almost surely, 2^66381861 is an apocalyptic number.

It is an amenable number.

66381861 is a deficient number, since it is larger than the sum of its proper divisors (42552923).

66381861 is a wasteful number, since it uses less digits than its factorization.

66381861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 243180.

The product of its digits is 41472, while the sum is 39.

The square root of 66381861 is about 8147.5064283497. The cubic root of 66381861 is about 404.9018936275.

The spelling of 66381861 in words is "sixty-six million, three hundred eighty-one thousand, eight hundred sixty-one".