21280751 has 8 divisors (see below), whose sum is σ = 22100880. Its totient is φ = 20466432.

The previous prime is 21280747. The next prime is 21280757. The reversal of 21280751 is 15708212.

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 21280751 - 2² = 21280747 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21280751.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21280757) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6911 + ... + 9503.

It is an arithmetic number, because the mean of its divisors is an integer number (2762610).

Almost surely, 2^21280751 is an apocalyptic number.

21280751 is a deficient number, since it is larger than the sum of its proper divisors (820129).

21280751 is a wasteful number, since it uses less digits than its factorization.

21280751 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2905.

The product of its (nonzero) digits is 1120, while the sum is 26.

The square root of 21280751 is about 4613.1064370985. The cubic root of 21280751 is about 277.1164563087.

Adding to 21280751 its reverse (15708212), we get a palindrome (36988963).

The spelling of 21280751 in words is "twenty-one million, two hundred eighty thousand, seven hundred fifty-one".