21321751 has 8 divisors (see below), whose sum is σ = 23418000. Its totient is φ = 19251840.

The previous prime is 21321749. The next prime is 21321779. The reversal of 21321751 is 15712312.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21321751 - 2¹ = 21321749 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 (21321551) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 4866 + ... + 8143.

It is an arithmetic number, because the mean of its divisors is an integer number (2927250).

Almost surely, 2^21321751 is an apocalyptic number.

21321751 is a deficient number, since it is larger than the sum of its proper divisors (2096249).

21321751 is a wasteful number, since it uses less digits than its factorization.

21321751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13169.

The product of its digits is 420, while the sum is 22.

The square root of 21321751 is about 4617.5481589259. The cubic root of 21321751 is about 277.2943085203.

It can be divided in two parts, 2132 and 1751, that added together give a palindrome (3883).

The spelling of 21321751 in words is "twenty-one million, three hundred twenty-one thousand, seven hundred fifty-one".