21630042 has 96 divisors (see below), whose sum is σ = 56609280. Its totient is φ = 5840640.

The previous prime is 21630031. The next prime is 21630061. The reversal of 21630042 is 24003612.

It is a happy number.

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

It is a junction number, because it is equal to n+sod(n) for n = 21629997 and 21630024.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 273759 + ... + 273837.

It is an arithmetic number, because the mean of its divisors is an integer number (589680).

Almost surely, 2^21630042 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21630042, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28304640).

21630042 is an abundant number, since it is smaller than the sum of its proper divisors (34979238).

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

21630042 is a wasteful number, since it uses less digits than its factorization.

21630042 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 188 (or 185 counting only the distinct ones).

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

The square root of 21630042 is about 4650.8108970372. The cubic root of 21630042 is about 278.6243837339.

Adding to 21630042 its reverse (24003612), we get a palindrome (45633654).

The spelling of 21630042 in words is "twenty-one million, six hundred thirty thousand, forty-two".