221908513 has 2 divisors, whose sum is σ = 221908514. Its totient is φ = 221908512.

The previous prime is 221908487. The next prime is 221908529. The reversal of 221908513 is 315809122.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 215267584 + 6640929 = 14672^2 + 2577^2 .

It is a cyclic number.

It is not a de Polignac number, because 221908513 - 2⁵ = 221908481 is a prime.

It is a super-3 number, since 3×221908513³ (a number of 26 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (221908553) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110954256 + 110954257.

It is an arithmetic number, because the mean of its divisors is an integer number (110954257).

Almost surely, 2^221908513 is an apocalyptic number.

It is an amenable number.

221908513 is a deficient number, since it is larger than the sum of its proper divisors (1).

221908513 is an equidigital number, since it uses as much as digits as its factorization.

221908513 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4320, while the sum is 31.

The square root of 221908513 is about 14896.5940066849. The cubic root of 221908513 is about 605.4217063063.

It can be divided in two parts, 22190 and 8513, that added together give a palindrome (30703).

The spelling of 221908513 in words is "two hundred twenty-one million, nine hundred eight thousand, five hundred thirteen".