66821557 has 8 divisors (see below), whose sum is σ = 73775520. Its totient is φ = 60014160.

The previous prime is 66821551. The next prime is 66821567. The reversal of 66821557 is 75512866.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 66821557 - 2⁷ = 66821429 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66821551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 35682 + ... + 37507.

It is an arithmetic number, because the mean of its divisors is an integer number (9221940).

Almost surely, 2^66821557 is an apocalyptic number.

It is an amenable number.

66821557 is a deficient number, since it is larger than the sum of its proper divisors (6953963).

66821557 is a wasteful number, since it uses less digits than its factorization.

66821557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73283.

The product of its digits is 100800, while the sum is 40.

The square root of 66821557 is about 8174.4453634482. The cubic root of 66821557 is about 405.7939149195.

The spelling of 66821557 in words is "sixty-six million, eight hundred twenty-one thousand, five hundred fifty-seven".