221957891 has 2 divisors, whose sum is σ = 221957892. Its totient is φ = 221957890.

The previous prime is 221957881. The next prime is 221957927. The reversal of 221957891 is 198759122.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-221957891 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (221957821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110978945 + 110978946.

It is an arithmetic number, because the mean of its divisors is an integer number (110978946).

Almost surely, 2^221957891 is an apocalyptic number.

221957891 is a deficient number, since it is larger than the sum of its proper divisors (1).

221957891 is an equidigital number, since it uses as much as digits as its factorization.

221957891 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 90720, while the sum is 44.

The square root of 221957891 is about 14898.2512732200. The cubic root of 221957891 is about 605.4666081378.

The spelling of 221957891 in words is "two hundred twenty-one million, nine hundred fifty-seven thousand, eight hundred ninety-one".