21831989 has 2 divisors, whose sum is σ = 21831990. Its totient is φ = 21831988.

The previous prime is 21831977. The next prime is 21832009. The reversal of 21831989 is 98913812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21003889 + 828100 = 4583^2 + 910^2 .

It is a cyclic number.

It is not a de Polignac number, because 21831989 - 2²⁴ = 5054773 is a prime.

It is a super-2 number, since 2×21831989² = 953271487392242, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21830989) 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, 10915994 + 10915995.

It is an arithmetic number, because the mean of its divisors is an integer number (10915995).

Almost surely, 2^21831989 is an apocalyptic number.

It is an amenable number.

21831989 is a deficient number, since it is larger than the sum of its proper divisors (1).

21831989 is an equidigital number, since it uses as much as digits as its factorization.

21831989 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 31104, while the sum is 41.

The square root of 21831989 is about 4672.4714017316. The cubic root of 21831989 is about 279.4888164726.

The spelling of 21831989 in words is "twenty-one million, eight hundred thirty-one thousand, nine hundred eighty-nine".