21540042 has 24 divisors (see below), whose sum is σ = 46758816. Its totient is φ = 7166376.

The previous prime is 21540023. The next prime is 21540049. The reversal of 21540042 is 24004512.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21539997 and 21540024.

It is not an unprimeable number, because it can be changed into a prime (21540049) by changing a digit.

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, 14163 + ... + 15609.

It is an arithmetic number, because the mean of its divisors is an integer number (1948284).

Almost surely, 2^21540042 is an apocalyptic number.

21540042 is an abundant number, since it is smaller than the sum of its proper divisors (25218774).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21540042 is a wasteful number, since it uses less digits than its factorization.

21540042 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2282 (or 2279 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 18.

The square root of 21540042 is about 4641.1250791161. The cubic root of 21540042 is about 278.2374056776.

Adding to 21540042 its reverse (24004512), we get a palindrome (45544554).

The spelling of 21540042 in words is "twenty-one million, five hundred forty thousand, forty-two".