21131028 has 18 divisors (see below), whose sum is σ = 53414634. Its totient is φ = 7043664.

The previous prime is 21131009. The next prime is 21131029. The reversal of 21131028 is 82013112.

It can be written as a sum of positive squares in only one way, i.e., 20629764 + 501264 = 4542^2 + 708^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a self number, because there is not a number n which added to its sum of digits gives 21131028.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21131029) by changing a digit.

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 5 ways as a sum of consecutive naturals, for example, 293451 + ... + 293522.

Almost surely, 2^21131028 is an apocalyptic number.

It is an amenable number.

21131028 is an abundant number, since it is smaller than the sum of its proper divisors (32283606).

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

21131028 is a wasteful number, since it uses less digits than its factorization.

21131028 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 586983 (or 586978 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 18.

The square root of 21131028 is about 4596.8497908894. The cubic root of 21131028 is about 276.4650320331.

The spelling of 21131028 in words is "twenty-one million, one hundred thirty-one thousand, twenty-eight".