420991 has 6 divisors (see below), whose sum is σ = 432240. Its totient is φ = 409968.

The previous prime is 420977. The next prime is 420997. The reversal of 420991 is 199024.

It is not a de Polignac number, because 420991 - 2⁹ = 420479 is a prime.

It is a Duffinian number.

420991 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (420997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 5290 + ... + 5368.

It is an arithmetic number, because the mean of its divisors is an integer number (72040).

2⁴²⁰⁹⁹¹ is an apocalyptic number.

420991 is a deficient number, since it is larger than the sum of its proper divisors (11249).

420991 is an frugal number, since it uses more digits than its factorization.

420991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 225 (or 152 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 25.

The square root of 420991 is about 648.8381924640. The cubic root of 420991 is about 74.9475781827.

The spelling of 420991 in words is "four hundred twenty thousand, nine hundred ninety-one".