21028501 has 6 divisors (see below), whose sum is σ = 22770690. Its totient is φ = 19410768.

The previous prime is 21028493. The next prime is 21028517. The reversal of 21028501 is 10582012.

It can be written as a sum of positive squares in 3 ways, for example, as 1887876 + 19140625 = 1374^2 + 4375^2 .

It is not a de Polignac number, because 21028501 - 2³ = 21028493 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21028001) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 62046 + ... + 62383.

It is an arithmetic number, because the mean of its divisors is an integer number (3795115).

Almost surely, 2^21028501 is an apocalyptic number.

It is an amenable number.

21028501 is a deficient number, since it is larger than the sum of its proper divisors (1742189).

21028501 is a wasteful number, since it uses less digits than its factorization.

21028501 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 124455 (or 124442 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 19.

The square root of 21028501 is about 4585.6843545975. The cubic root of 21028501 is about 276.0171740696.

The spelling of 21028501 in words is "twenty-one million, twenty-eight thousand, five hundred one".