21280743 has 24 divisors (see below), whose sum is σ = 34320000. Its totient is φ = 12594960.

The previous prime is 21280739. The next prime is 21280747. The reversal of 21280743 is 34708212.

It is an interprime number because it is at equal distance from previous prime (21280739) and next prime (21280747).

It is not a de Polignac number, because 21280743 - 2² = 21280739 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21280747) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1758 + ... + 6756.

It is an arithmetic number, because the mean of its divisors is an integer number (1430000).

Almost surely, 2^21280743 is an apocalyptic number.

21280743 is a deficient number, since it is larger than the sum of its proper divisors (13039257).

21280743 is a wasteful number, since it uses less digits than its factorization.

21280743 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5059 (or 5056 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 27.

The square root of 21280743 is about 4613.1055700038. The cubic root of 21280743 is about 277.1164215836.

Adding to 21280743 its reverse (34708212), we get a palindrome (55988955).

The spelling of 21280743 in words is "twenty-one million, two hundred eighty thousand, seven hundred forty-three".