21120751 has 4 divisors (see below), whose sum is σ = 21211632. Its totient is φ = 21029872.

The previous prime is 21120733. The next prime is 21120763. The reversal of 21120751 is 15702112.

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 21120751 - 2¹⁹ = 20596463 is a prime.

It is a super-2 number, since 2×21120751² = 892172245608002, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21120721) 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, 45091 + ... + 45556.

It is an arithmetic number, because the mean of its divisors is an integer number (5302908).

Almost surely, 2^21120751 is an apocalyptic number.

21120751 is a deficient number, since it is larger than the sum of its proper divisors (90881).

21120751 is an equidigital number, since it uses as much as digits as its factorization.

21120751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90880.

The product of its (nonzero) digits is 140, while the sum is 19.

The square root of 21120751 is about 4595.7318242038. The cubic root of 21120751 is about 276.4202055050.

Adding to 21120751 its reverse (15702112), we get a palindrome (36822863).

The spelling of 21120751 in words is "twenty-one million, one hundred twenty thousand, seven hundred fifty-one".