21212375 has 16 divisors (see below), whose sum is σ = 27125280. Its totient is φ = 16552000.

The previous prime is 21212353. The next prime is 21212423. The reversal of 21212375 is 57321212.

It is a happy number.

It is not a de Polignac number, because 21212375 - 2⁸ = 21212119 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21212375.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3056 + ... + 7194.

It is an arithmetic number, because the mean of its divisors is an integer number (1695330).

Almost surely, 2^21212375 is an apocalyptic number.

21212375 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21212375 is a deficient number, since it is larger than the sum of its proper divisors (5912905).

21212375 is an equidigital number, since it uses as much as digits as its factorization.

21212375 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4195 (or 4185 counting only the distinct ones).

The product of its digits is 840, while the sum is 23.

The square root of 21212375 is about 4605.6894163632. The cubic root of 21212375 is about 276.8193420319.

Adding to 21212375 its reverse (57321212), we get a palindrome (78533587).

The spelling of 21212375 in words is "twenty-one million, two hundred twelve thousand, three hundred seventy-five".