21311250 has 40 divisors (see below), whose sum is σ = 53270448. Its totient is φ = 5682000.

The previous prime is 21311249. The next prime is 21311261. The reversal of 21311250 is 5211312.

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

It is a Curzon number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 909 + ... + 6591.

Almost surely, 2^21311250 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21311250, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26635224).

21311250 is an abundant number, since it is smaller than the sum of its proper divisors (31959198).

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

21311250 is an equidigital number, since it uses as much as digits as its factorization.

21311250 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5708 (or 5693 counting only the distinct ones).

The product of its (nonzero) digits is 60, while the sum is 15.

The square root of 21311250 is about 4616.4109435794. The cubic root of 21311250 is about 277.2487783995.

Adding to 21311250 its reverse (5211312), we get a palindrome (26522562).

The spelling of 21311250 in words is "twenty-one million, three hundred eleven thousand, two hundred fifty".