21391463 has 4 divisors (see below), whose sum is σ = 21913248. Its totient is φ = 20869680.

The previous prime is 21391451. The next prime is 21391471. The reversal of 21391463 is 36419312.

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

It is a cyclic number.

It is not a de Polignac number, because 21391463 - 2⁶ = 21391399 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 (21390463) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 260831 + ... + 260912.

It is an arithmetic number, because the mean of its divisors is an integer number (5478312).

Almost surely, 2^21391463 is an apocalyptic number.

21391463 is a deficient number, since it is larger than the sum of its proper divisors (521785).

21391463 is an equidigital number, since it uses as much as digits as its factorization.

21391463 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 521784.

The product of its digits is 3888, while the sum is 29.

The square root of 21391463 is about 4625.0905937073. The cubic root of 21391463 is about 277.5961866599.

The spelling of 21391463 in words is "twenty-one million, three hundred ninety-one thousand, four hundred sixty-three".