21242040 has 64 divisors (see below), whose sum is σ = 64087200. Its totient is φ = 5632512.

The previous prime is 21241991. The next prime is 21242047. The reversal of 21242040 is 4024212.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21242047) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 27094 + ... + 27866.

Almost surely, 2^21242040 is an apocalyptic number.

21242040 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21242040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32043600).

21242040 is an abundant number, since it is smaller than the sum of its proper divisors (42845160).

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

21242040 is a wasteful number, since it uses less digits than its factorization.

21242040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1016 (or 1012 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 15.

The square root of 21242040 is about 4608.9087645559. The cubic root of 21242040 is about 276.9483236716.

Adding to 21242040 its reverse (4024212), we get a palindrome (25266252).

The spelling of 21242040 in words is "twenty-one million, two hundred forty-two thousand, forty".