66138555 has 16 divisors (see below), whose sum is σ = 120939264. Its totient is φ = 30234720.

The previous prime is 66138539. The next prime is 66138557. The reversal of 66138555 is 55583166.

It is not a de Polignac number, because 66138555 - 2⁴ = 66138539 is a prime.

It is not an unprimeable number, because it can be changed into a prime (66138557) 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, 314841 + ... + 315050.

It is an arithmetic number, because the mean of its divisors is an integer number (7558704).

Almost surely, 2^66138555 is an apocalyptic number.

66138555 is a deficient number, since it is larger than the sum of its proper divisors (54800709).

66138555 is a wasteful number, since it uses less digits than its factorization.

66138555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 629906.

The product of its digits is 108000, while the sum is 39.

The square root of 66138555 is about 8132.5614046252. The cubic root of 66138555 is about 404.4065993556.

The spelling of 66138555 in words is "sixty-six million, one hundred thirty-eight thousand, five hundred fifty-five".