21020042 has 16 divisors (see below), whose sum is σ = 33300960. Its totient is φ = 9923472.

The previous prime is 21020039. The next prime is 21020053. The reversal of 21020042 is 24002012.

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 7 ways as a sum of consecutive naturals, for example, 13433 + ... + 14915.

It is an arithmetic number, because the mean of its divisors is an integer number (2081310).

Almost surely, 2^21020042 is an apocalyptic number.

21020042 is a deficient number, since it is larger than the sum of its proper divisors (12280918).

21020042 is a wasteful number, since it uses less digits than its factorization.

21020042 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1877.

The product of its (nonzero) digits is 32, while the sum is 11.

The square root of 21020042 is about 4584.7619349318. The cubic root of 21020042 is about 275.9801585540.

Adding to 21020042 its reverse (24002012), we get a palindrome (45022054).

The spelling of 21020042 in words is "twenty-one million, twenty thousand, forty-two".