66556121 has 4 divisors (see below), whose sum is σ = 66690000. Its totient is φ = 66422244.

The previous prime is 66556117. The next prime is 66556141. The reversal of 66556121 is 12165566.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 66556121 - 2² = 66556117 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66556111) 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, 66191 + ... + 67188.

It is an arithmetic number, because the mean of its divisors is an integer number (16672500).

Almost surely, 2^66556121 is an apocalyptic number.

It is an amenable number.

66556121 is a deficient number, since it is larger than the sum of its proper divisors (133879).

66556121 is a wasteful number, since it uses less digits than its factorization.

66556121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 133878.

The product of its digits is 10800, while the sum is 32.

The square root of 66556121 is about 8158.1934887572. The cubic root of 66556121 is about 405.2558886882.

The spelling of 66556121 in words is "sixty-six million, five hundred fifty-six thousand, one hundred twenty-one".