21310542 has 48 divisors (see below), whose sum is σ = 51562368. Its totient is φ = 6305040.

The previous prime is 21310519. The next prime is 21310561. The reversal of 21310542 is 24501312.

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

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 23 ways as a sum of consecutive naturals, for example, 7263 + ... + 9765.

It is an arithmetic number, because the mean of its divisors is an integer number (1074216).

Almost surely, 2^21310542 is an apocalyptic number.

21310542 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 21310542, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25781184).

21310542 is an abundant number, since it is smaller than the sum of its proper divisors (30251826).

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

21310542 is a wasteful number, since it uses less digits than its factorization.

21310542 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2565 (or 2562 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21310542 is about 4616.3342599946. The cubic root of 21310542 is about 277.2457081227.

Adding to 21310542 its reverse (24501312), we get a palindrome (45811854).

The spelling of 21310542 in words is "twenty-one million, three hundred ten thousand, five hundred forty-two".