221660639 has 2 divisors, whose sum is σ = 221660640. Its totient is φ = 221660638.

The previous prime is 221660627. The next prime is 221660689. The reversal of 221660639 is 936066122.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 221660639 - 2⁴ = 221660623 is a prime.

It is a Sophie Germain prime.

It is a junction number, because it is equal to n+sod(n) for n = 221660599 and 221660608.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221660609) 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, 110830319 + 110830320.

It is an arithmetic number, because the mean of its divisors is an integer number (110830320).

Almost surely, 2^221660639 is an apocalyptic number.

221660639 is a deficient number, since it is larger than the sum of its proper divisors (1).

221660639 is an equidigital number, since it uses as much as digits as its factorization.

221660639 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 23328, while the sum is 35.

The square root of 221660639 is about 14888.2718607634. The cubic root of 221660639 is about 605.1962016473.

It can be divided in two parts, 22 and 1660639, that added together give a palindrome (1660661).

The spelling of 221660639 in words is "two hundred twenty-one million, six hundred sixty thousand, six hundred thirty-nine".