21000542 has 16 divisors (see below), whose sum is σ = 33445872. Its totient is φ = 9855360.

The previous prime is 21000533. The next prime is 21000557. The reversal of 21000542 is 24500012.

21000542 is a modest number, since divided by 542 gives 210 as remainder.

It is a congruent number.

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, 17192 + ... + 18372.

It is an arithmetic number, because the mean of its divisors is an integer number (2090367).

Almost surely, 2^21000542 is an apocalyptic number.

21000542 is a deficient number, since it is larger than the sum of its proper divisors (12445330).

21000542 is a wasteful number, since it uses less digits than its factorization.

21000542 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1723.

The product of its (nonzero) digits is 80, while the sum is 14.

The square root of 21000542 is about 4582.6348316225. The cubic root of 21000542 is about 275.8947911683.

Adding to 21000542 its reverse (24500012), we get a palindrome (45500554).

The spelling of 21000542 in words is "twenty-one million, five hundred forty-two", and thus it is an aban number.