21531043 has 2 divisors, whose sum is σ = 21531044. Its totient is φ = 21531042.

The previous prime is 21531023. The next prime is 21531049. The reversal of 21531043 is 34013512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21531043 - 2⁵ = 21531011 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21531043.

It is not a weakly prime, because it can be changed into another prime (21531049) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10765521 + 10765522.

It is an arithmetic number, because the mean of its divisors is an integer number (10765522).

Almost surely, 2^21531043 is an apocalyptic number.

21531043 is a deficient number, since it is larger than the sum of its proper divisors (1).

21531043 is an equidigital number, since it uses as much as digits as its factorization.

21531043 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 360, while the sum is 19.

The square root of 21531043 is about 4640.1554930843. The cubic root of 21531043 is about 278.1986529339.

Adding to 21531043 its reverse (34013512), we get a palindrome (55544555).

The spelling of 21531043 in words is "twenty-one million, five hundred thirty-one thousand, forty-three".