21420842 has 16 divisors (see below), whose sum is σ = 32768064. Its totient is φ = 10500000.

The previous prime is 21420827. The next prime is 21420859. The reversal of 21420842 is 24802412.

It is a happy number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 35342 + ... + 35942.

It is an arithmetic number, because the mean of its divisors is an integer number (2048004).

Almost surely, 2^21420842 is an apocalyptic number.

21420842 is a deficient number, since it is larger than the sum of its proper divisors (11347222).

21420842 is a wasteful number, since it uses less digits than its factorization.

21420842 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 925.

The product of its (nonzero) digits is 1024, while the sum is 23.

The square root of 21420842 is about 4628.2655498577. The cubic root of 21420842 is about 277.7232119071.

The spelling of 21420842 in words is "twenty-one million, four hundred twenty thousand, eight hundred forty-two".