21340242 has 96 divisors (see below), whose sum is σ = 58631040. Its totient is φ = 5448960.

The previous prime is 21340223. The next prime is 21340243. The reversal of 21340242 is 24204312.

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

It is not an unprimeable number, because it can be changed into a prime (21340243) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 123268 + ... + 123440.

It is an arithmetic number, because the mean of its divisors is an integer number (610740).

Almost surely, 2^21340242 is an apocalyptic number.

21340242 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 21340242, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29315520).

21340242 is an abundant number, since it is smaller than the sum of its proper divisors (37290798).

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

21340242 is a wasteful number, since it uses less digits than its factorization.

21340242 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 288 (or 285 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 18.

The square root of 21340242 is about 4619.5499780823. The cubic root of 21340242 is about 277.3744452710.

Adding to 21340242 its reverse (24204312), we get a palindrome (45544554).

It can be divided in two parts, 213402 and 42, that added together give a square (213444 = 462²).

The spelling of 21340242 in words is "twenty-one million, three hundred forty thousand, two hundred forty-two".