21042270 has 96 divisors (see below), whose sum is σ = 57620160. Its totient is φ = 5322240.

The previous prime is 21042251. The next prime is 21042283. The reversal of 21042270 is 7224012.

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

It is a Curzon number.

It is a congruent number.

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, 236386 + ... + 236474.

It is an arithmetic number, because the mean of its divisors is an integer number (600210).

Almost surely, 2^21042270 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21042270, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28810080).

21042270 is an abundant number, since it is smaller than the sum of its proper divisors (36577890).

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

21042270 is a wasteful number, since it uses less digits than its factorization.

21042270 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 210 (or 207 counting only the distinct ones).

The product of its (nonzero) digits is 224, while the sum is 18.

The square root of 21042270 is about 4587.1854115569. The cubic root of 21042270 is about 276.0774042509.

Adding to 21042270 its reverse (7224012), we get a palindrome (28266282).

It can be divided in two parts, 21042 and 270, that added together give a palindrome (21312).

The spelling of 21042270 in words is "twenty-one million, forty-two thousand, two hundred seventy".