21115542 has 64 divisors (see below), whose sum is σ = 50125824. Its totient is φ = 5806080.

The previous prime is 21115511. The next prime is 21115559. The reversal of 21115542 is 24551112.

It is a super-2 number, since 2×21115542² = 891732227907528, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 217638 + ... + 217734.

It is an arithmetic number, because the mean of its divisors is an integer number (783216).

Almost surely, 2^21115542 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21115542, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25062912).

21115542 is an abundant number, since it is smaller than the sum of its proper divisors (29010282).

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

21115542 is a wasteful number, since it uses less digits than its factorization.

21115542 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 253.

The product of its digits is 400, while the sum is 21.

The square root of 21115542 is about 4595.1650677642. The cubic root of 21115542 is about 276.3974791786.

Adding to 21115542 its reverse (24551112), we get a palindrome (45666654).

It can be divided in two parts, 211 and 15542, that added together give a triangular number (15753 = T₁₇₇).

The spelling of 21115542 in words is "twenty-one million, one hundred fifteen thousand, five hundred forty-two".