20216591 has 2 divisors, whose sum is σ = 20216592. Its totient is φ = 20216590.

The previous prime is 20216569. The next prime is 20216593. The reversal of 20216591 is 19561202.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20216591 is a prime.

It is a super-2 number, since 2×20216591² = 817421103322562, which contains 22 as substring.

Together with 20216593, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20216591.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20216593) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10108295 + 10108296.

It is an arithmetic number, because the mean of its divisors is an integer number (10108296).

Almost surely, 2^20216591 is an apocalyptic number.

20216591 is a deficient number, since it is larger than the sum of its proper divisors (1).

20216591 is an equidigital number, since it uses as much as digits as its factorization.

20216591 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1080, while the sum is 26.

The square root of 20216591 is about 4496.2863565391. The cubic root of 20216591 is about 272.4181096692.

Adding to 20216591 its reverse (19561202), we get a palindrome (39777793).

The spelling of 20216591 in words is "twenty million, two hundred sixteen thousand, five hundred ninety-one".