66815814 has 64 divisors (see below), whose sum is σ = 156219840. Its totient is φ = 18862080.

The previous prime is 66815803. The next prime is 66815873. The reversal of 66815814 is 41851866.

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

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 53752 + ... + 54980.

It is an arithmetic number, because the mean of its divisors is an integer number (2440935).

Almost surely, 2^66815814 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 66815814, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (78109920).

66815814 is an abundant number, since it is smaller than the sum of its proper divisors (89404026).

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

66815814 is a wasteful number, since it uses less digits than its factorization.

66815814 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1305.

The product of its digits is 46080, while the sum is 39.

The square root of 66815814 is about 8174.0940782450. The cubic root of 66815814 is about 405.7822892240.

The spelling of 66815814 in words is "sixty-six million, eight hundred fifteen thousand, eight hundred fourteen".