21085428 has 48 divisors (see below), whose sum is σ = 60556160. Its totient is φ = 5560704.

The previous prime is 21085409. The next prime is 21085453. The reversal of 21085428 is 82458012.

It is a junction number, because it is equal to n+sod(n) for n = 21085395 and 21085404.

It is a congruent number.

It is an unprimeable number.

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 in 15 ways as a sum of consecutive naturals, for example, 8563 + ... + 10746.

Almost surely, 2^21085428 is an apocalyptic number.

21085428 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21085428 is an abundant number, since it is smaller than the sum of its proper divisors (39470732).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21085428 is a wasteful number, since it uses less digits than its factorization.

21085428 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19336 (or 19334 counting only the distinct ones).

The product of its (nonzero) digits is 5120, while the sum is 30.

The square root of 21085428 is about 4591.8871937364. The cubic root of 21085428 is about 276.2660216065.

The spelling of 21085428 in words is "twenty-one million, eighty-five thousand, four hundred twenty-eight".