221996521 has 2 divisors, whose sum is σ = 221996522. Its totient is φ = 221996520.

The previous prime is 221996519. The next prime is 221996561. The reversal of 221996521 is 125699122.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 214915600 + 7080921 = 14660^2 + 2661^2 .

It is a cyclic number.

It is not a de Polignac number, because 221996521 - 2¹ = 221996519 is a prime.

It is a super-2 number, since 2×221996521² = 98564910672206882, which contains 22 as substring.

Together with 221996519, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (221996561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110998260 + 110998261.

It is an arithmetic number, because the mean of its divisors is an integer number (110998261).

Almost surely, 2^221996521 is an apocalyptic number.

It is an amenable number.

221996521 is a deficient number, since it is larger than the sum of its proper divisors (1).

221996521 is an equidigital number, since it uses as much as digits as its factorization.

221996521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 19440, while the sum is 37.

The square root of 221996521 is about 14899.5476776981. The cubic root of 221996521 is about 605.5017316443.

The spelling of 221996521 in words is "two hundred twenty-one million, nine hundred ninety-six thousand, five hundred twenty-one".