217949940 has 240 divisors, whose sum is σ = 751322880. Its totient is φ = 52565760.

The previous prime is 217949887. The next prime is 217949947. The reversal of 217949940 is 49949712.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (217949947) by changing a digit.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 1663675 + ... + 1663805.

It is an arithmetic number, because the mean of its divisors is an integer number (3130512).

Almost surely, 2^217949940 is an apocalyptic number.

217949940 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 217949940, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (375661440).

217949940 is an abundant number, since it is smaller than the sum of its proper divisors (533372940).

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

217949940 is a wasteful number, since it uses less digits than its factorization.

217949940 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 244 (or 233 counting only the distinct ones).

The product of its (nonzero) digits is 163296, while the sum is 45.

The square root of 217949940 is about 14763.1277173911. The cubic root of 217949940 is about 601.8000940349.

The spelling of 217949940 in words is "two hundred seventeen million, nine hundred forty-nine thousand, nine hundred forty".