21800521 has 2 divisors, whose sum is σ = 21800522. Its totient is φ = 21800520.

The previous prime is 21800509. The next prime is 21800551. The reversal of 21800521 is 12500812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21492496 + 308025 = 4636^2 + 555^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21800521 is a prime.

It is not a weakly prime, because it can be changed into another prime (21800551) 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 as a sum of consecutive naturals, namely, 10900260 + 10900261.

It is an arithmetic number, because the mean of its divisors is an integer number (10900261).

Almost surely, 2^21800521 is an apocalyptic number.

It is an amenable number.

21800521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21800521 is an equidigital number, since it uses as much as digits as its factorization.

21800521 is an odious number, because the sum of its binary digits is odd.

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

The square root of 21800521 is about 4669.1028046082. The cubic root of 21800521 is about 279.3544695278.

The spelling of 21800521 in words is "twenty-one million, eight hundred thousand, five hundred twenty-one".