21353751 has 24 divisors (see below), whose sum is σ = 32853600. Its totient is φ = 13318656.

The previous prime is 21353737. The next prime is 21353767. The reversal of 21353751 is 15735312.

It is not a de Polignac number, because 21353751 - 2¹⁴ = 21337367 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21353711) 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 23 ways as a sum of consecutive naturals, for example, 35350 + ... + 35948.

It is an arithmetic number, because the mean of its divisors is an integer number (1368900).

Almost surely, 2^21353751 is an apocalyptic number.

21353751 is a deficient number, since it is larger than the sum of its proper divisors (11499849).

21353751 is a wasteful number, since it uses less digits than its factorization.

21353751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 855 (or 852 counting only the distinct ones).

The product of its digits is 3150, while the sum is 27.

The square root of 21353751 is about 4621.0119021703. The cubic root of 21353751 is about 277.4329616489.

It can be divided in two parts, 2135 and 3751, that added together give a triangular number (5886 = T₁₀₈).

The spelling of 21353751 in words is "twenty-one million, three hundred fifty-three thousand, seven hundred fifty-one".