21006342 has 48 divisors (see below), whose sum is σ = 52284960. Its totient is φ = 5970816.

The previous prime is 21006341. The next prime is 21006379. The reversal of 21006342 is 24360012.

It is a happy number.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21006341) 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, 36634 + ... + 37202.

It is an arithmetic number, because the mean of its divisors is an integer number (1089270).

Almost surely, 2^21006342 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21006342, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26142480).

21006342 is an abundant number, since it is smaller than the sum of its proper divisors (31278618).

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

21006342 is a wasteful number, since it uses less digits than its factorization.

21006342 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 877 (or 874 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 21006342 is about 4583.2676116500. The cubic root of 21006342 is about 275.9201880128.

Adding to 21006342 its reverse (24360012), we get a palindrome (45366354).

The spelling of 21006342 in words is "twenty-one million, six thousand, three hundred forty-two".