421991891 has 2 divisors, whose sum is σ = 421991892. Its totient is φ = 421991890.

The previous prime is 421991873. The next prime is 421991939. The reversal of 421991891 is 198199124.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 421991891 - 2⁶ = 421991827 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (421991821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 210995945 + 210995946.

It is an arithmetic number, because the mean of its divisors is an integer number (210995946).

Almost surely, 2^421991891 is an apocalyptic number.

421991891 is a deficient number, since it is larger than the sum of its proper divisors (1).

421991891 is an equidigital number, since it uses as much as digits as its factorization.

421991891 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 46656, while the sum is 44.

The square root of 421991891 is about 20542.4412132541. The cubic root of 421991891 is about 750.0692623442.

The spelling of 421991891 in words is "four hundred twenty-one million, nine hundred ninety-one thousand, eight hundred ninety-one".