21845531 has 2 divisors, whose sum is σ = 21845532. Its totient is φ = 21845530.

The previous prime is 21845521. The next prime is 21845533. The reversal of 21845531 is 13554812.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21845531 - 2¹⁴ = 21829147 is a prime.

It is a super-2 number, since 2×21845531² = 954454449343922, which contains 22 as substring.

Together with 21845533, 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 = 21845494 and 21845503.

It is not a weakly prime, because it can be changed into another prime (21845533) 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, 10922765 + 10922766.

It is an arithmetic number, because the mean of its divisors is an integer number (10922766).

Almost surely, 2^21845531 is an apocalyptic number.

21845531 is a deficient number, since it is larger than the sum of its proper divisors (1).

21845531 is an equidigital number, since it uses as much as digits as its factorization.

21845531 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4800, while the sum is 29.

The square root of 21845531 is about 4673.9203031288. The cubic root of 21845531 is about 279.5465918661.

The spelling of 21845531 in words is "twenty-one million, eight hundred forty-five thousand, five hundred thirty-one".