21245751 has 12 divisors (see below), whose sum is σ = 31192200. Its totient is φ = 13931280.

The previous prime is 21245747. The next prime is 21245753. The reversal of 21245751 is 15754212.

It is not a de Polignac number, because 21245751 - 2² = 21245747 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21245753) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 18801 + ... + 19898.

It is an arithmetic number, because the mean of its divisors is an integer number (2599350).

Almost surely, 2^21245751 is an apocalyptic number.

21245751 is a deficient number, since it is larger than the sum of its proper divisors (9946449).

21245751 is a wasteful number, since it uses less digits than its factorization.

21245751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38766 (or 38763 counting only the distinct ones).

The product of its digits is 2800, while the sum is 27.

The square root of 21245751 is about 4609.3113368485. The cubic root of 21245751 is about 276.9644504244.

Adding to 21245751 its reverse (15754212), we get a palindrome (36999963).

It can be divided in two parts, 2124 and 5751, that added together give a triangular number (7875 = T₁₂₅).

The spelling of 21245751 in words is "twenty-one million, two hundred forty-five thousand, seven hundred fifty-one".