21531023 has 2 divisors, whose sum is σ = 21531024. Its totient is φ = 21531022.

The previous prime is 21531011. The next prime is 21531043. The reversal of 21531023 is 32013512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21531023 - 2¹⁶ = 21465487 is a prime.

It is a zygodrome in base 3.

It is a junction number, because it is equal to n+sod(n) for n = 21530992 and 21531010.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21531043) 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, 10765511 + 10765512.

It is an arithmetic number, because the mean of its divisors is an integer number (10765512).

Almost surely, 2^21531023 is an apocalyptic number.

21531023 is a deficient number, since it is larger than the sum of its proper divisors (1).

21531023 is an equidigital number, since it uses as much as digits as its factorization.

21531023 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 180, while the sum is 17.

The square root of 21531023 is about 4640.1533379836. The cubic root of 21531023 is about 278.1985667951.

Adding to 21531023 its reverse (32013512), we get a palindrome (53544535).

The spelling of 21531023 in words is "twenty-one million, five hundred thirty-one thousand, twenty-three".