999999421 has 4 divisors (see below), whose sum is σ = 1000106332. Its totient is φ = 999892512.

The previous prime is 999999391. The next prime is 999999433. The reversal of 999999421 is 124999999.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 124999999 = 499 ⋅250501.

It can be written as a sum of positive squares in 2 ways, for example, as 728244196 + 271755225 = 26986^2 + 16485^2 .

It is a cyclic number.

It is not a de Polignac number, because 999999421 - 2¹³ = 999991229 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 10.

It is a self number, because there is not a number n which added to its sum of digits gives 999999421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (999999491) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 37920 + ... + 58633.

It is an arithmetic number, because the mean of its divisors is an integer number (250026583).

Almost surely, 2^999999421 is an apocalyptic number.

It is an amenable number.

999999421 is a deficient number, since it is larger than the sum of its proper divisors (106911).

999999421 is a wasteful number, since it uses less digits than its factorization.

999999421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 106910.

The product of its digits is 4251528, while the sum is 61.

The square root of 999999421 is about 31622.7674468886. The cubic root of 999999421 is about 999.9998070000. Note that the first 3 decimals are identical.

The spelling of 999999421 in words is "nine hundred ninety-nine million, nine hundred ninety-nine thousand, four hundred twenty-one".