421639 has 2 divisors, whose sum is σ = 421640. Its totient is φ = 421638.

The previous prime is 421633. The next prime is 421643. The reversal of 421639 is 936124.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 421639 - 2⁵ = 421607 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (421633) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 210819 + 210820.

It is an arithmetic number, because the mean of its divisors is an integer number (210820).

2⁴²¹⁶³⁹ is an apocalyptic number.

421639 is a deficient number, since it is larger than the sum of its proper divisors (1).

421639 is an equidigital number, since it uses as much as digits as its factorization.

421639 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1296, while the sum is 25.

The square root of 421639 is about 649.3373545392. The cubic root of 421639 is about 74.9860122062.

It can be divided in two parts, 42 and 1639, that added together give a square (1681 = 41²).

The spelling of 421639 in words is "four hundred twenty-one thousand, six hundred thirty-nine".