216475821 has 48 divisors (see below), whose sum is σ = 338732160. Its totient is φ = 138305880.

The previous prime is 216475817. The next prime is 216475823. The reversal of 216475821 is 128574612.

216475821 is a `hidden beast` number, since 2 + 1 + 647 + 5 + 8 + 2 + 1 = 666.

It is not a de Polignac number, because 216475821 - 2² = 216475817 is a prime.

It is a super-3 number, since 3×216475821³ (a number of 26 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216475823) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 2101656 + ... + 2101758.

It is an arithmetic number, because the mean of its divisors is an integer number (7056920).

Almost surely, 2^216475821 is an apocalyptic number.

It is an amenable number.

216475821 is a deficient number, since it is larger than the sum of its proper divisors (122256339).

216475821 is an frugal number, since it uses more digits than its factorization.

216475821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 186 (or 137 counting only the distinct ones).

The product of its digits is 26880, while the sum is 36.

The square root of 216475821 is about 14713.1173107537. The cubic root of 216475821 is about 600.4402518848.

The spelling of 216475821 in words is "two hundred sixteen million, four hundred seventy-five thousand, eight hundred twenty-one".