21212140 has 24 divisors (see below), whose sum is σ = 45278352. Its totient is φ = 8345280.

The previous prime is 21212131. The next prime is 21212143. The reversal of 21212140 is 4121212.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21212140.

It is not an unprimeable number, because it can be changed into a prime (21212143) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7474 + ... + 9913.

It is an arithmetic number, because the mean of its divisors is an integer number (1886598).

Almost surely, 2^21212140 is an apocalyptic number.

21212140 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21212140 is an abundant number, since it is smaller than the sum of its proper divisors (24066212).

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

21212140 is a wasteful number, since it uses less digits than its factorization.

21212140 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17457 (or 17455 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 13.

The square root of 21212140 is about 4605.6639043682. The cubic root of 21212140 is about 276.8183197861.

Adding to 21212140 its reverse (4121212), we get a palindrome (25333352).

The spelling of 21212140 in words is "twenty-one million, two hundred twelve thousand, one hundred forty".