217131840 has 140 divisors (see below), whose sum is σ = 772468356. Its totient is φ = 57894912.

The previous prime is 217131823. The next prime is 217131853. The reversal of 217131840 is 48131712.

It can be written as a sum of positive squares in 2 ways, for example, as 52881984 + 164249856 = 7272^2 + 12816^2 .

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 21732 + ... + 30108.

Almost surely, 2^217131840 is an apocalyptic number.

217131840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 217131840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (386234178).

217131840 is an abundant number, since it is smaller than the sum of its proper divisors (555336516).

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

217131840 is an equidigital number, since it uses as much as digits as its factorization.

217131840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8406 (or 8387 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 27.

The square root of 217131840 is about 14735.3941243524. The cubic root of 217131840 is about 601.0461748036.

The spelling of 217131840 in words is "two hundred seventeen million, one hundred thirty-one thousand, eight hundred forty".