21018642 has 32 divisors (see below), whose sum is σ = 44126208. Its totient is φ = 6661776.

The previous prime is 21018631. The next prime is 21018659. The reversal of 21018642 is 24681012.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 30433 + ... + 31115.

It is an arithmetic number, because the mean of its divisors is an integer number (1378944).

Almost surely, 2^21018642 is an apocalyptic number.

21018642 is an abundant number, since it is smaller than the sum of its proper divisors (23107566).

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

21018642 is a wasteful number, since it uses less digits than its factorization.

21018642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 934.

The product of its (nonzero) digits is 768, while the sum is 24.

The square root of 21018642 is about 4584.6092527063. The cubic root of 21018642 is about 275.9740313731.

Adding to 21018642 its reverse (24681012), we get a palindrome (45699654).

The spelling of 21018642 in words is "twenty-one million, eighteen thousand, six hundred forty-two".