20028521 has 2 divisors, whose sum is σ = 20028522. Its totient is φ = 20028520.

The previous prime is 20028517. The next prime is 20028523. The reversal of 20028521 is 12582002.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12250000 + 7778521 = 3500^2 + 2789^2 .

It is a cyclic number.

It is not a de Polignac number, because 20028521 - 2² = 20028517 is a prime.

It is a super-2 number, since 2×20028521² = 802283306894882, which contains 22 as substring.

Together with 20028523, it forms a pair of twin primes.

It is a Chen prime.

It is equal to p_1272314 and since 20028521 and 1272314 have the same sum of digits, it is a Honaker prime.

It is a junction number, because it is equal to n+sod(n) for n = 20028493 and 20028502.

It is not a weakly prime, because it can be changed into another prime (20028523) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10014260 + 10014261.

It is an arithmetic number, because the mean of its divisors is an integer number (10014261).

Almost surely, 2^20028521 is an apocalyptic number.

It is an amenable number.

20028521 is a deficient number, since it is larger than the sum of its proper divisors (1).

20028521 is an equidigital number, since it uses as much as digits as its factorization.

20028521 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 320, while the sum is 20.

The square root of 20028521 is about 4475.3235637214. The cubic root of 20028521 is about 271.5707302151.

The spelling of 20028521 in words is "twenty million, twenty-eight thousand, five hundred twenty-one".