21550901 has 2 divisors, whose sum is σ = 21550902. Its totient is φ = 21550900.

The previous prime is 21550891. The next prime is 21550937. The reversal of 21550901 is 10905512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18054001 + 3496900 = 4249^2 + 1870^2 .

It is a cyclic number.

It is not a de Polignac number, because 21550901 - 2¹⁰ = 21549877 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21550201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10775450 + 10775451.

It is an arithmetic number, because the mean of its divisors is an integer number (10775451).

Almost surely, 2^21550901 is an apocalyptic number.

It is an amenable number.

21550901 is a deficient number, since it is larger than the sum of its proper divisors (1).

21550901 is an equidigital number, since it uses as much as digits as its factorization.

21550901 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 450, while the sum is 23.

The square root of 21550901 is about 4642.2947989114. The cubic root of 21550901 is about 278.2841538441.

The spelling of 21550901 in words is "twenty-one million, five hundred fifty thousand, nine hundred one".