216639973 has 12 divisors (see below), whose sum is σ = 240812460. Its totient is φ = 194722880.

The previous prime is 216639953. The next prime is 216639989. The reversal of 216639973 is 379936612.

It can be written as a sum of positive squares in 2 ways, for example, as 43270084 + 173369889 = 6578^2 + 13167^2 .

It is a de Polignac number, because none of the positive numbers 2^k-216639973 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216639923) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 711 + ... + 20827.

It is an arithmetic number, because the mean of its divisors is an integer number (20067705).

Almost surely, 2^216639973 is an apocalyptic number.

It is an amenable number.

216639973 is a deficient number, since it is larger than the sum of its proper divisors (24172487).

216639973 is a wasteful number, since it uses less digits than its factorization.

216639973 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20228 (or 20217 counting only the distinct ones).

The product of its digits is 367416, while the sum is 46.

The square root of 216639973 is about 14718.6946771784. The cubic root of 216639973 is about 600.5919833267.

The spelling of 216639973 in words is "two hundred sixteen million, six hundred thirty-nine thousand, nine hundred seventy-three".