216731021 has 8 divisors (see below), whose sum is σ = 233580984. Its totient is φ = 199906560.

The previous prime is 216731003. The next prime is 216731023. The reversal of 216731021 is 120137612.

It can be written as a sum of positive squares in 4 ways, for example, as 26152996 + 190578025 = 5114^2 + 13805^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 216731021 - 2²⁶ = 149622157 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216731023) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13625 + ... + 24881.

It is an arithmetic number, because the mean of its divisors is an integer number (29197623).

Almost surely, 2^216731021 is an apocalyptic number.

It is an amenable number.

216731021 is a deficient number, since it is larger than the sum of its proper divisors (16849963).

216731021 is a wasteful number, since it uses less digits than its factorization.

216731021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12751.

The product of its (nonzero) digits is 504, while the sum is 23.

The square root of 216731021 is about 14721.7872895923. The cubic root of 216731021 is about 600.6761091375.

Adding to 216731021 its reverse (120137612), we get a palindrome (336868633).

The spelling of 216731021 in words is "two hundred sixteen million, seven hundred thirty-one thousand, twenty-one".