21017828 has 12 divisors (see below), whose sum is σ = 39610620. Its totient is φ = 9700512.

The previous prime is 21017809. The next prime is 21017861. The reversal of 21017828 is 82871012.

It can be written as a sum of positive squares in 2 ways, for example, as 2630884 + 18386944 = 1622^2 + 4288^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21017828.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 202043 + ... + 202146.

It is an arithmetic number, because the mean of its divisors is an integer number (3300885).

Almost surely, 2^21017828 is an apocalyptic number.

It is an amenable number.

21017828 is a deficient number, since it is larger than the sum of its proper divisors (18592792).

21017828 is a wasteful number, since it uses less digits than its factorization.

21017828 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 404206 (or 404204 counting only the distinct ones).

The product of its (nonzero) digits is 1792, while the sum is 29.

The square root of 21017828 is about 4584.5204765602. The cubic root of 21017828 is about 275.9704687300.

The spelling of 21017828 in words is "twenty-one million, seventeen thousand, eight hundred twenty-eight".