21240534 has 16 divisors (see below), whose sum is σ = 48549888. Its totient is φ = 6068712.

The previous prime is 21240529. The next prime is 21240539. The reversal of 21240534 is 43504212.

It is an interprime number because it is at equal distance from previous prime (21240529) and next prime (21240539).

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

It is a self number, because there is not a number n which added to its sum of digits gives 21240534.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21240539) 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 7 ways as a sum of consecutive naturals, for example, 252822 + ... + 252905.

It is an arithmetic number, because the mean of its divisors is an integer number (3034368).

Almost surely, 2^21240534 is an apocalyptic number.

21240534 is an abundant number, since it is smaller than the sum of its proper divisors (27309354).

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

21240534 is a wasteful number, since it uses less digits than its factorization.

21240534 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 505739.

The product of its (nonzero) digits is 960, while the sum is 21.

The square root of 21240534 is about 4608.7453824224. The cubic root of 21240534 is about 276.9417785684.

Adding to 21240534 its reverse (43504212), we get a palindrome (64744746).

The spelling of 21240534 in words is "twenty-one million, two hundred forty thousand, five hundred thirty-four".