21005342 has 4 divisors (see below), whose sum is σ = 31508016. Its totient is φ = 10502670.

The previous prime is 21005339. The next prime is 21005363. The reversal of 21005342 is 24350012.

It is a semiprime because it is the product of two primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21005342.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5251334 + ... + 5251337.

It is an arithmetic number, because the mean of its divisors is an integer number (7877004).

Almost surely, 2^21005342 is an apocalyptic number.

21005342 is a deficient number, since it is larger than the sum of its proper divisors (10502674).

21005342 is a wasteful number, since it uses less digits than its factorization.

21005342 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10502673.

The product of its (nonzero) digits is 240, while the sum is 17.

The square root of 21005342 is about 4583.1585178783. The cubic root of 21005342 is about 275.9158095801.

Adding to 21005342 its reverse (24350012), we get a palindrome (45355354).

The spelling of 21005342 in words is "twenty-one million, five thousand, three hundred forty-two".