21212240 has 40 divisors (see below), whose sum is σ = 56365440. Its totient is φ = 7272576.

The previous prime is 21212239. The next prime is 21212263. The reversal of 21212240 is 4221212.

It is a tau number, because it is divible by the number of its divisors (40).

It is a Harshad number since it is a multiple of its sum of digits (14).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18380 + ... + 19499.

It is an arithmetic number, because the mean of its divisors is an integer number (1409136).

Almost surely, 2^21212240 is an apocalyptic number.

21212240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21212240 is an abundant number, since it is smaller than the sum of its proper divisors (35153200).

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

21212240 is a wasteful number, since it uses less digits than its factorization.

21212240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37899 (or 37893 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 14.

The square root of 21212240 is about 4605.6747605535. The cubic root of 21212240 is about 276.8187547852.

Adding to 21212240 its reverse (4221212), we get a palindrome (25433452).

The spelling of 21212240 in words is "twenty-one million, two hundred twelve thousand, two hundred forty".