21089969 has 2 divisors, whose sum is σ = 21089970. Its totient is φ = 21089968.

The previous prime is 21089953. The next prime is 21089983. The reversal of 21089969 is 96998012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20976400 + 113569 = 4580^2 + 337^2 .

It is a cyclic number.

It is not a de Polignac number, because 21089969 - 2⁴ = 21089953 is a prime.

It is a super-2 number, since 2×21089969² = 889573584841922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21089569) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10544984 + 10544985.

It is an arithmetic number, because the mean of its divisors is an integer number (10544985).

Almost surely, 2^21089969 is an apocalyptic number.

It is an amenable number.

21089969 is a deficient number, since it is larger than the sum of its proper divisors (1).

21089969 is an equidigital number, since it uses as much as digits as its factorization.

21089969 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 69984, while the sum is 44.

The square root of 21089969 is about 4592.3816261282. The cubic root of 21089969 is about 276.2858525842.

The spelling of 21089969 in words is "twenty-one million, eighty-nine thousand, nine hundred sixty-nine".