21256312 has 48 divisors (see below), whose sum is σ = 50082480. Its totient is φ = 8279040.

The previous prime is 21256309. The next prime is 21256321. The reversal of 21256312 is 21365212.

It is a Harshad number since it is a multiple of its sum of digits (22).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5208 + ... + 8344.

It is an arithmetic number, because the mean of its divisors is an integer number (1043385).

Almost surely, 2^21256312 is an apocalyptic number.

21256312 is a gapful number since it is divisible by the number (22) 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 21256312, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25041240).

21256312 is an abundant number, since it is smaller than the sum of its proper divisors (28826168).

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

21256312 is a wasteful number, since it uses less digits than its factorization.

21256312 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3172 (or 3157 counting only the distinct ones).

The product of its digits is 720, while the sum is 22.

The square root of 21256312 is about 4610.4568103389. The cubic root of 21256312 is about 277.0103346898.

Subtracting 21256312 from its reverse (21365212), we obtain a square (108900 = 330²).

The spelling of 21256312 in words is "twenty-one million, two hundred fifty-six thousand, three hundred twelve".