21751312 has 40 divisors (see below), whose sum is σ = 46559520. Its totient is φ = 9761280.

The previous prime is 21751291. The next prime is 21751337. The reversal of 21751312 is 21315712.

It is a happy number.

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

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 7 ways as a sum of consecutive naturals, for example, 13864 + ... + 15352.

It is an arithmetic number, because the mean of its divisors is an integer number (1163988).

Almost surely, 2^21751312 is an apocalyptic number.

21751312 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 21751312, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23279760).

21751312 is an abundant number, since it is smaller than the sum of its proper divisors (24808208).

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

21751312 is a wasteful number, since it uses less digits than its factorization.

21751312 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1591 (or 1585 counting only the distinct ones).

The product of its digits is 420, while the sum is 22.

The square root of 21751312 is about 4663.8301855878. The cubic root of 21751312 is about 279.1441211861.

Subtracting from 21751312 its reverse (21315712), we obtain a square (435600 = 660²).

It can be divided in two parts, 217 and 51312, that added together give a square (51529 = 227²).

The spelling of 21751312 in words is "twenty-one million, seven hundred fifty-one thousand, three hundred twelve".