216500021 has 2 divisors, whose sum is σ = 216500022. Its totient is φ = 216500020.

The previous prime is 216499999. The next prime is 216500047. The reversal of 216500021 is 120005612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 215796100 + 703921 = 14690^2 + 839^2 .

It is a cyclic number.

It is not a de Polignac number, because 216500021 - 2⁶ = 216499957 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (216500521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108250010 + 108250011.

It is an arithmetic number, because the mean of its divisors is an integer number (108250011).

Almost surely, 2^216500021 is an apocalyptic number.

It is an amenable number.

216500021 is a deficient number, since it is larger than the sum of its proper divisors (1).

216500021 is an equidigital number, since it uses as much as digits as its factorization.

216500021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 120, while the sum is 17.

The square root of 216500021 is about 14713.9396831712. The cubic root of 216500021 is about 600.4626256116.

Adding to 216500021 its reverse (120005612), we get a palindrome (336505633).

The spelling of 216500021 in words is "two hundred sixteen million, five hundred thousand, twenty-one".