21136542 has 48 divisors (see below), whose sum is σ = 52079760. Its totient is φ = 5682432.

The previous prime is 21136541. The next prime is 21136543. The reversal of 21136542 is 24563112.

It is an interprime number because it is at equal distance from previous prime (21136541) and next prime (21136543).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21136541) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2884 + ... + 7112.

It is an arithmetic number, because the mean of its divisors is an integer number (1084995).

Almost surely, 2^21136542 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21136542, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26039880).

21136542 is an abundant number, since it is smaller than the sum of its proper divisors (30943218).

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

21136542 is a wasteful number, since it uses less digits than its factorization.

21136542 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4265 (or 4258 counting only the distinct ones).

The product of its digits is 1440, while the sum is 24.

The square root of 21136542 is about 4597.4495103264. The cubic root of 21136542 is about 276.4890771736.

Adding to 21136542 its reverse (24563112), we get a palindrome (45699654).

The spelling of 21136542 in words is "twenty-one million, one hundred thirty-six thousand, five hundred forty-two".