217664840 has 16 divisors (see below), whose sum is σ = 489745980. Its totient is φ = 87065920.

The previous prime is 217664833. The next prime is 217664851. The reversal of 217664840 is 48466712.

217664840 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 209496676 + 8168164 = 14474^2 + 2858^2 .

It is a junction number, because it is equal to n+sod(n) for n = 217664794 and 217664803.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2720771 + ... + 2720850.

Almost surely, 2^217664840 is an apocalyptic number.

217664840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

217664840 is an abundant number, since it is smaller than the sum of its proper divisors (272081140).

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

217664840 is a wasteful number, since it uses less digits than its factorization.

217664840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5441632 (or 5441628 counting only the distinct ones).

The product of its (nonzero) digits is 64512, while the sum is 38.

The square root of 217664840 is about 14753.4687446715. The cubic root of 217664840 is about 601.5375749250.

The spelling of 217664840 in words is "two hundred seventeen million, six hundred sixty-four thousand, eight hundred forty".