21234728 has 16 divisors (see below), whose sum is σ = 41188500. Its totient is φ = 10251136.

The previous prime is 21234713. The next prime is 21234767. The reversal of 21234728 is 82743212.

It can be written as a sum of positive squares in 2 ways, for example, as 19166884 + 2067844 = 4378^2 + 1438^2 .

It is a Harshad number since it is a multiple of its sum of digits (29).

It is a self number, because there is not a number n which added to its sum of digits gives 21234728.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 45533 + ... + 45996.

Almost surely, 2^21234728 is an apocalyptic number.

It is an amenable number.

21234728 is a deficient number, since it is larger than the sum of its proper divisors (19953772).

21234728 is a wasteful number, since it uses less digits than its factorization.

21234728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 91564 (or 91560 counting only the distinct ones).

The product of its digits is 5376, while the sum is 29.

The square root of 21234728 is about 4608.1154499426. The cubic root of 21234728 is about 276.9165426917.

The spelling of 21234728 in words is "twenty-one million, two hundred thirty-four thousand, seven hundred twenty-eight".