216511826021 has 4 divisors (see below), whose sum is σ = 216518115852. Its totient is φ = 216505536192.

The previous prime is 216511825987. The next prime is 216511826033. The reversal of 216511826021 is 120628115612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 150866212225 + 65645613796 = 388415^2 + 256214^2 .

It is a cyclic number.

It is not a de Polignac number, because 216511826021 - 2¹⁴ = 216511809637 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 (216511826071) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3092996 + ... + 3162221.

It is an arithmetic number, because the mean of its divisors is an integer number (54129528963).

Almost surely, 2^216511826021 is an apocalyptic number.

It is an amenable number.

216511826021 is a deficient number, since it is larger than the sum of its proper divisors (6289831).

216511826021 is an equidigital number, since it uses as much as digits as its factorization.

216511826021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6289830.

The product of its (nonzero) digits is 11520, while the sum is 35.

The spelling of 216511826021 in words is "two hundred sixteen billion, five hundred eleven million, eight hundred twenty-six thousand, twenty-one".