21945042 has 72 divisors (see below), whose sum is σ = 56019600. Its totient is φ = 6190128.

The previous prime is 21945029. The next prime is 21945043. The reversal of 21945042 is 24054912.

It is a junction number, because it is equal to n+sod(n) for n = 21944997 and 21945015.

It is not an unprimeable number, because it can be changed into a prime (21945043) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 122509 + ... + 122687.

It is an arithmetic number, because the mean of its divisors is an integer number (778050).

Almost surely, 2^21945042 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21945042, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28009800).

21945042 is an abundant number, since it is smaller than the sum of its proper divisors (34074558).

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

21945042 is a wasteful number, since it uses less digits than its factorization.

21945042 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 340 (or 330 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 27.

The square root of 21945042 is about 4684.5535539686. The cubic root of 21945042 is about 279.9704135405.

Adding to 21945042 its reverse (24054912), we get a palindrome (45999954).

The spelling of 21945042 in words is "twenty-one million, nine hundred forty-five thousand, forty-two".