28721738 has 8 divisors (see below), whose sum is σ = 45616932. Its totient is φ = 13516096.

The previous prime is 28721723. The next prime is 28721743. The reversal of 28721738 is 83712782.

It can be written as a sum of positive squares in 2 ways, for example, as 21501769 + 7219969 = 4637^2 + 2687^2 .

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 422345 + ... + 422412.

Almost surely, 2^28721738 is an apocalyptic number.

28721738 is a deficient number, since it is larger than the sum of its proper divisors (16895194).

28721738 is a wasteful number, since it uses less digits than its factorization.

28721738 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 844776.

The product of its digits is 37632, while the sum is 38.

The square root of 28721738 is about 5359.2665542964. The cubic root of 28721738 is about 306.2458687212.

The spelling of 28721738 in words is "twenty-eight million, seven hundred twenty-one thousand, seven hundred thirty-eight".