21726751 has 4 divisors (see below), whose sum is σ = 21763504. Its totient is φ = 21690000.

The previous prime is 21726721. The next prime is 21726791. The reversal of 21726751 is 15762712.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21726751 - 2¹⁹ = 21202463 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21726701) 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 3 ways as a sum of consecutive naturals, for example, 17475 + ... + 18676.

It is an arithmetic number, because the mean of its divisors is an integer number (5440876).

Almost surely, 2^21726751 is an apocalyptic number.

21726751 is a deficient number, since it is larger than the sum of its proper divisors (36753).

21726751 is an equidigital number, since it uses as much as digits as its factorization.

21726751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36752.

The product of its digits is 5880, while the sum is 31.

The square root of 21726751 is about 4661.1963056709. The cubic root of 21726751 is about 279.0390142553.

It can be divided in two parts, 2172675 and 1, that added together give a square (2172676 = 1474²).

The spelling of 21726751 in words is "twenty-one million, seven hundred twenty-six thousand, seven hundred fifty-one".