216840405 has 16 divisors (see below), whose sum is σ = 351126720. Its totient is φ = 114254208.

The previous prime is 216840397. The next prime is 216840413. The reversal of 216840405 is 504048612.

It is an interprime number because it is at equal distance from previous prime (216840397) and next prime (216840413).

It is not a de Polignac number, because 216840405 - 2³ = 216840397 is a prime.

It is a super-2 number, since 2×216840405² = 94039522481128050, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 85840 + ... + 88329.

It is an arithmetic number, because the mean of its divisors is an integer number (21945420).

Almost surely, 2^216840405 is an apocalyptic number.

It is an amenable number.

216840405 is a deficient number, since it is larger than the sum of its proper divisors (134286315).

216840405 is a wasteful number, since it uses less digits than its factorization.

216840405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 174260.

The product of its (nonzero) digits is 7680, while the sum is 30.

The square root of 216840405 is about 14725.5018590199. The cubic root of 216840405 is about 600.7771457507. Note that the first 3 decimals are identical.

The spelling of 216840405 in words is "two hundred sixteen million, eight hundred forty thousand, four hundred five".