216213921 has 96 divisors (see below), whose sum is σ = 413683200. Its totient is φ = 110345760.

The previous prime is 216213917. The next prime is 216213929. The reversal of 216213921 is 129312612.

216213921 is a `hidden beast` number, since 2 + 1 + 621 + 39 + 2 + 1 = 666.

It is not a de Polignac number, because 216213921 - 2² = 216213917 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216213929) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 1207810 + ... + 1207988.

It is an arithmetic number, because the mean of its divisors is an integer number (4309200).

Almost surely, 2^216213921 is an apocalyptic number.

216213921 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

216213921 is a deficient number, since it is larger than the sum of its proper divisors (197469279).

216213921 is a wasteful number, since it uses less digits than its factorization.

216213921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 296 (or 283 counting only the distinct ones).

The product of its digits is 1296, while the sum is 27.

The square root of 216213921 is about 14704.2143958798. The cubic root of 216213921 is about 600.1980096464.

It can be divided in two parts, 2162139 and 21, that added together give a triangular number (2162160 = T₂₀₇₉).

The spelling of 216213921 in words is "two hundred sixteen million, two hundred thirteen thousand, nine hundred twenty-one".