21531463 has 4 divisors (see below), whose sum is σ = 21601008. Its totient is φ = 21461920.

The previous prime is 21531443. The next prime is 21531479. The reversal of 21531463 is 36413512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21531463 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21531443) 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 in 3 ways as a sum of consecutive naturals, for example, 34306 + ... + 34927.

It is an arithmetic number, because the mean of its divisors is an integer number (5400252).

Almost surely, 2^21531463 is an apocalyptic number.

21531463 is a deficient number, since it is larger than the sum of its proper divisors (69545).

21531463 is an equidigital number, since it uses as much as digits as its factorization.

21531463 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 69544.

The product of its digits is 2160, while the sum is 25.

The square root of 21531463 is about 4640.2007499676. The cubic root of 21531463 is about 278.2004618364.

Adding to 21531463 its reverse (36413512), we get a palindrome (57944975).

The spelling of 21531463 in words is "twenty-one million, five hundred thirty-one thousand, four hundred sixty-three".