221671691 has 2 divisors, whose sum is σ = 221671692. Its totient is φ = 221671690.

The previous prime is 221671657. The next prime is 221671717. The reversal of 221671691 is 196176122.

221671691 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-221671691 is a prime.

It is not a weakly prime, because it can be changed into another prime (221671601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110835845 + 110835846.

It is an arithmetic number, because the mean of its divisors is an integer number (110835846).

Almost surely, 2^221671691 is an apocalyptic number.

221671691 is a deficient number, since it is larger than the sum of its proper divisors (1).

221671691 is an equidigital number, since it uses as much as digits as its factorization.

221671691 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9072, while the sum is 35.

The square root of 221671691 is about 14888.6430207726. The cubic root of 221671691 is about 605.2062598415.

The spelling of 221671691 in words is "two hundred twenty-one million, six hundred seventy-one thousand, six hundred ninety-one".