66665790 has 72 divisors (see below), whose sum is σ = 177002280. Its totient is φ = 17407872.

The previous prime is 66665777. The next prime is 66665803. The reversal of 66665790 is 9756666.

It is an interprime number because it is at equal distance from previous prime (66665777) and next prime (66665803).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 479541 + ... + 479679.

It is an arithmetic number, because the mean of its divisors is an integer number (2458365).

Almost surely, 2^66665790 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 66665790, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (88501140).

66665790 is an abundant number, since it is smaller than the sum of its proper divisors (110336490).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

66665790 is a wasteful number, since it uses less digits than its factorization.

66665790 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 298 (or 222 counting only the distinct ones).

The product of its (nonzero) digits is 408240, while the sum is 45.

The square root of 66665790 is about 8164.9121244506. The cubic root of 66665790 is about 405.4783556759.

It can be divided in two parts, 66 and 665790, that added together give a square (665856 = 816²).

The spelling of 66665790 in words is "sixty-six million, six hundred sixty-five thousand, seven hundred ninety".