21428385 has 32 divisors (see below), whose sum is σ = 38033280. Its totient is φ = 10214400.

The previous prime is 21428383. The next prime is 21428389. The reversal of 21428385 is 58382412.

It is not a de Polignac number, because 21428385 - 2¹ = 21428383 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is not an unprimeable number, because it can be changed into a prime (21428383) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 9001 + ... + 11129.

It is an arithmetic number, because the mean of its divisors is an integer number (1188540).

Almost surely, 2^21428385 is an apocalyptic number.

It is an amenable number.

21428385 is a deficient number, since it is larger than the sum of its proper divisors (16604895).

21428385 is a wasteful number, since it uses less digits than its factorization.

21428385 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2209.

The product of its digits is 15360, while the sum is 33.

The square root of 21428385 is about 4629.0803622318. The cubic root of 21428385 is about 277.7558066474.

The spelling of 21428385 in words is "twenty-one million, four hundred twenty-eight thousand, three hundred eighty-five".