221638679 has 2 divisors, whose sum is σ = 221638680. Its totient is φ = 221638678.

The previous prime is 221638657. The next prime is 221638717. The reversal of 221638679 is 976836122.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 221638679 - 2⁸ = 221638423 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221638609) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110819339 + 110819340.

It is an arithmetic number, because the mean of its divisors is an integer number (110819340).

Almost surely, 2^221638679 is an apocalyptic number.

221638679 is a deficient number, since it is larger than the sum of its proper divisors (1).

221638679 is an equidigital number, since it uses as much as digits as its factorization.

221638679 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 217728, while the sum is 44.

The square root of 221638679 is about 14887.5343492467. The cubic root of 221638679 is about 605.1762153181.

The spelling of 221638679 in words is "two hundred twenty-one million, six hundred thirty-eight thousand, six hundred seventy-nine".