217990388 has 144 divisors (see below), whose sum is σ = 528138240. Its totient is φ = 76377600.

The previous prime is 217990379. The next prime is 217990397. The reversal of 217990388 is 883099712.

It is an interprime number because it is at equal distance from previous prime (217990379) and next prime (217990397).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 2759333 + ... + 2759411.

Almost surely, 2^217990388 is an apocalyptic number.

217990388 is a gapful number since it is divisible by the number (28) 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 217990388, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (264069120).

217990388 is an abundant number, since it is smaller than the sum of its proper divisors (310147852).

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

217990388 is a wasteful number, since it uses less digits than its factorization.

217990388 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 166 (or 147 counting only the distinct ones).

The product of its (nonzero) digits is 217728, while the sum is 47.

The square root of 217990388 is about 14764.4975532525. The cubic root of 217990388 is about 601.8373198685.

The spelling of 217990388 in words is "two hundred seventeen million, nine hundred ninety thousand, three hundred eighty-eight".