21428578 has 4 divisors (see below), whose sum is σ = 32142870. Its totient is φ = 10714288.

The previous prime is 21428549. The next prime is 21428579. The reversal of 21428578 is 87582412.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 21095649 + 332929 = 4593^2 + 577^2 .

It is not an unprimeable number, because it can be changed into a prime (21428579) 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 as a sum of consecutive naturals, namely, 5357143 + ... + 5357146.

Almost surely, 2^21428578 is an apocalyptic number.

21428578 is a deficient number, since it is larger than the sum of its proper divisors (10714292).

21428578 is a wasteful number, since it uses less digits than its factorization.

21428578 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10714291.

The product of its digits is 35840, while the sum is 37.

The square root of 21428578 is about 4629.1012086581. The cubic root of 21428578 is about 277.7566405368.

The spelling of 21428578 in words is "twenty-one million, four hundred twenty-eight thousand, five hundred seventy-eight".