221512861 has 2 divisors, whose sum is σ = 221512862. Its totient is φ = 221512860.

The previous prime is 221512859. The next prime is 221512877. The reversal of 221512861 is 168215122.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 219217636 + 2295225 = 14806^2 + 1515^2 .

It is a cyclic number.

It is not a de Polignac number, because 221512861 - 2¹ = 221512859 is a prime.

Together with 221512859, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221512891) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110756430 + 110756431.

It is an arithmetic number, because the mean of its divisors is an integer number (110756431).

Almost surely, 2^221512861 is an apocalyptic number.

It is an amenable number.

221512861 is a deficient number, since it is larger than the sum of its proper divisors (1).

221512861 is an equidigital number, since it uses as much as digits as its factorization.

221512861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1920, while the sum is 28.

The square root of 221512861 is about 14883.3081336106. The cubic root of 221512861 is about 605.0616798441.

Adding to 221512861 its reverse (168215122), we get a palindrome (389727983).

The spelling of 221512861 in words is "two hundred twenty-one million, five hundred twelve thousand, eight hundred sixty-one".