21312040 has 16 divisors (see below), whose sum is σ = 47952180. Its totient is φ = 8524800.

The previous prime is 21312023. The next prime is 21312059. The reversal of 21312040 is 4021312.

It can be written as a sum of positive squares in 2 ways, for example, as 20629764 + 682276 = 4542^2 + 826^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21312040.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 266361 + ... + 266440.

Almost surely, 2^21312040 is an apocalyptic number.

21312040 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21312040 is an abundant number, since it is smaller than the sum of its proper divisors (26640140).

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

21312040 is a wasteful number, since it uses less digits than its factorization.

21312040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 532812 (or 532808 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 21312040 is about 4616.4965070928. The cubic root of 21312040 is about 277.2522041930.

Adding to 21312040 its reverse (4021312), we get a palindrome (25333352).

The spelling of 21312040 in words is "twenty-one million, three hundred twelve thousand, forty".