21223540 has 24 divisors (see below), whose sum is σ = 47998440. Its totient is φ = 7836288.

The previous prime is 21223519. The next prime is 21223583. The reversal of 21223540 is 4532212.

It can be written as a sum of positive squares in 4 ways, for example, as 1527696 + 19695844 = 1236^2 + 4438^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 40555 + ... + 41074.

It is an arithmetic number, because the mean of its divisors is an integer number (1999935).

Almost surely, 2^21223540 is an apocalyptic number.

21223540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21223540 is an abundant number, since it is smaller than the sum of its proper divisors (26774900).

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

21223540 is a wasteful number, since it uses less digits than its factorization.

21223540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81651 (or 81649 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 19.

The square root of 21223540 is about 4606.9013447219. The cubic root of 21223540 is about 276.8679008858.

Adding to 21223540 its reverse (4532212), we get a palindrome (25755752).

The spelling of 21223540 in words is "twenty-one million, two hundred twenty-three thousand, five hundred forty".