21089531 has 2 divisors, whose sum is σ = 21089532. Its totient is φ = 21089530.

The previous prime is 21089521. The next prime is 21089533. The reversal of 21089531 is 13598012.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21089531 is a prime.

It is a super-2 number, since 2×21089531² = 889536635599922, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 21089533, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21089494 and 21089503.

It is not a weakly prime, because it can be changed into another prime (21089533) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10544765 + 10544766.

It is an arithmetic number, because the mean of its divisors is an integer number (10544766).

Almost surely, 2^21089531 is an apocalyptic number.

21089531 is a deficient number, since it is larger than the sum of its proper divisors (1).

21089531 is an equidigital number, since it uses as much as digits as its factorization.

21089531 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2160, while the sum is 29.

The square root of 21089531 is about 4592.3339382061. Note that the first 3 decimals coincide. The cubic root of 21089531 is about 276.2839399207.

The spelling of 21089531 in words is "twenty-one million, eighty-nine thousand, five hundred thirty-one".