66581797 has 4 divisors (see below), whose sum is σ = 66608460. Its totient is φ = 66555136.

The previous prime is 66581791. The next prime is 66581807. The reversal of 66581797 is 79718566.

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 23561316 + 43020481 = 4854^2 + 6559^2 .

It is a cyclic number.

It is not a de Polignac number, because 66581797 - 2¹⁵ = 66549029 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 66581797.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66581791) 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, 9148 + ... + 14725.

It is an arithmetic number, because the mean of its divisors is an integer number (16652115).

Almost surely, 2^66581797 is an apocalyptic number.

It is an amenable number.

66581797 is a deficient number, since it is larger than the sum of its proper divisors (26663).

66581797 is a wasteful number, since it uses less digits than its factorization.

66581797 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26662.

The product of its digits is 635040, while the sum is 49.

The square root of 66581797 is about 8159.7669697118. The cubic root of 66581797 is about 405.3079951525.

The spelling of 66581797 in words is "sixty-six million, five hundred eighty-one thousand, seven hundred ninety-seven".