21406042 has 24 divisors (see below), whose sum is σ = 37701396. Its totient is φ = 9088128.

The previous prime is 21406037. The next prime is 21406069. The reversal of 21406042 is 24060412.

It can be written as a sum of positive squares in 2 ways, for example, as 20259001 + 1147041 = 4501^2 + 1071^2 .

It is an unprimeable number.

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 in 11 ways as a sum of consecutive naturals, for example, 10108 + ... + 12040.

Almost surely, 2^21406042 is an apocalyptic number.

21406042 is a deficient number, since it is larger than the sum of its proper divisors (16295354).

21406042 is a wasteful number, since it uses less digits than its factorization.

21406042 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2062 (or 2055 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 19.

The square root of 21406042 is about 4626.6664024976. Note that the first 3 decimals coincide. The cubic root of 21406042 is about 277.6592360447.

Adding to 21406042 its reverse (24060412), we get a palindrome (45466454).

The spelling of 21406042 in words is "twenty-one million, four hundred six thousand, forty-two".