21112506 has 24 divisors (see below), whose sum is σ = 45842004. Its totient is φ = 7022400.

The previous prime is 21112433. The next prime is 21112547. The reversal of 21112506 is 60521112.

It can be written as a sum of positive squares in 2 ways, for example, as 15280281 + 5832225 = 3909^2 + 2415^2 .

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

It is a Curzon number.

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 11 ways as a sum of consecutive naturals, for example, 10156 + ... + 12056.

Almost surely, 2^21112506 is an apocalyptic number.

21112506 is an abundant number, since it is smaller than the sum of its proper divisors (24729498).

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

21112506 is a wasteful number, since it uses less digits than its factorization.

21112506 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2526 (or 2523 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 18.

The square root of 21112506 is about 4594.8347086702. The cubic root of 21112506 is about 276.3842317017.

Adding to 21112506 its reverse (60521112), we get a palindrome (81633618).

The spelling of 21112506 in words is "twenty-one million, one hundred twelve thousand, five hundred six".