21312522 has 48 divisors (see below), whose sum is σ = 57575232. Its totient is φ = 5535360.

The previous prime is 21312517. The next prime is 21312523. The reversal of 21312522 is 22521312.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21312495 and 21312504.

It is not an unprimeable number, because it can be changed into a prime (21312523) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 6303 + ... + 9074.

It is an arithmetic number, because the mean of its divisors is an integer number (1199484).

Almost surely, 2^21312522 is an apocalyptic number.

21312522 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

21312522 is an abundant number, since it is smaller than the sum of its proper divisors (36262710).

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

21312522 is a wasteful number, since it uses less digits than its factorization.

21312522 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15403 (or 15400 counting only the distinct ones).

The product of its digits is 240, while the sum is 18.

The square root of 21312522 is about 4616.5487108878. The cubic root of 21312522 is about 277.2542943191.

Adding to 21312522 its reverse (22521312), we get a palindrome (43833834).

The spelling of 21312522 in words is "twenty-one million, three hundred twelve thousand, five hundred twenty-two".