66320820 has 54 divisors (see below), whose sum is σ = 201505122. Its totient is φ = 17656416.

The previous prime is 66320809. The next prime is 66320833. The reversal of 66320820 is 2802366.

66320820 is a `hidden beast` number, since 6 + 632 + 0 + 8 + 20 = 666.

It can be written as a sum of positive squares in only one way, i.e., 53056656 + 13264164 = 7284^2 + 3642^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 108957 + ... + 109563.

Almost surely, 2^66320820 is an apocalyptic number.

66320820 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

66320820 is an abundant number, since it is smaller than the sum of its proper divisors (135184302).

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

66320820 is a wasteful number, since it uses less digits than its factorization.

66320820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1229 (or 617 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 66320820 is about 8143.7595740542. The cubic root of 66320820 is about 404.7777472835. Note that the first 4 decimals are identical.

The spelling of 66320820 in words is "sixty-six million, three hundred twenty thousand, eight hundred twenty".