21531222 has 24 divisors (see below), whose sum is σ = 46736976. Its totient is φ = 7163856.

The previous prime is 21531193. The next prime is 21531233. The reversal of 21531222 is 22213512.

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 = 21531195 and 21531204.

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, 16788 + ... + 18024.

It is an arithmetic number, because the mean of its divisors is an integer number (1947374).

Almost surely, 2^21531222 is an apocalyptic number.

21531222 is an abundant number, since it is smaller than the sum of its proper divisors (25205754).

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

21531222 is a wasteful number, since it uses less digits than its factorization.

21531222 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2212 (or 2209 counting only the distinct ones).

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

The square root of 21531222 is about 4640.1747811909. The cubic root of 21531222 is about 278.1994238738.

Adding to 21531222 its reverse (22213512), we get a palindrome (43744734).

It can be divided in two parts, 2153 and 1222, that added together give a cube (3375 = 15³).

The spelling of 21531222 in words is "twenty-one million, five hundred thirty-one thousand, two hundred twenty-two".