217172820 has 48 divisors (see below), whose sum is σ = 615424320. Its totient is φ = 57213696.

The previous prime is 217172803. The next prime is 217172821. The reversal of 217172820 is 28271712.

It is a happy number.

217172820 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (217172821) 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, 16825 + ... + 26784.

It is an arithmetic number, because the mean of its divisors is an integer number (12821340).

Almost surely, 2^217172820 is an apocalyptic number.

217172820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

217172820 is an abundant number, since it is smaller than the sum of its proper divisors (398251500).

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

217172820 is a wasteful number, since it uses less digits than its factorization.

217172820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 43704 (or 43702 counting only the distinct ones).

The product of its (nonzero) digits is 3136, while the sum is 30.

The square root of 217172820 is about 14736.7845882336. The cubic root of 217172820 is about 601.0839848930.

The spelling of 217172820 in words is "two hundred seventeen million, one hundred seventy-two thousand, eight hundred twenty".