21242751 has 8 divisors (see below), whose sum is σ = 28344960. Its totient is φ = 14151192.

The previous prime is 21242747. The next prime is 21242759. The reversal of 21242751 is 15724212.

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

It is not a de Polignac number, because 21242751 - 2² = 21242747 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21242759) 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 7 ways as a sum of consecutive naturals, for example, 6646 + ... + 9308.

It is an arithmetic number, because the mean of its divisors is an integer number (3543120).

Almost surely, 2^21242751 is an apocalyptic number.

21242751 is a deficient number, since it is larger than the sum of its proper divisors (7102209).

21242751 is a wasteful number, since it uses less digits than its factorization.

21242751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5325.

The product of its digits is 1120, while the sum is 24.

The square root of 21242751 is about 4608.9858971362. The cubic root of 21242751 is about 276.9514135830.

Adding to 21242751 its reverse (15724212), we get a palindrome (36966963).

The spelling of 21242751 in words is "twenty-one million, two hundred forty-two thousand, seven hundred fifty-one".