66239820 has 72 divisors (see below), whose sum is σ = 212756544. Its totient is φ = 16624128.

The previous prime is 66239819. The next prime is 66239821. The reversal of 66239820 is 2893266.

66239820 is a `hidden beast` number, since 6 + 623 + 9 + 8 + 20 = 666.

It is an interprime number because it is at equal distance from previous prime (66239819) and next prime (66239821).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (66239821) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 7764 + ... + 13883.

It is an arithmetic number, because the mean of its divisors is an integer number (2954952).

Almost surely, 2^66239820 is an apocalyptic number.

66239820 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

66239820 is an abundant number, since it is smaller than the sum of its proper divisors (146516724).

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

66239820 is a wasteful number, since it uses less digits than its factorization.

66239820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21679 (or 21674 counting only the distinct ones).

The product of its (nonzero) digits is 31104, while the sum is 36.

The square root of 66239820 is about 8138.7849215961. The cubic root of 66239820 is about 404.6128902819.

The spelling of 66239820 in words is "sixty-six million, two hundred thirty-nine thousand, eight hundred twenty".