21997263 has 4 divisors (see below), whose sum is σ = 29329688. Its totient is φ = 14664840.

The previous prime is 21997253. The next prime is 21997301. The reversal of 21997263 is 36279912.

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

It is not a de Polignac number, because 21997263 - 2¹⁶ = 21931727 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 (21997243) 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, 3666208 + ... + 3666213.

It is an arithmetic number, because the mean of its divisors is an integer number (7332422).

Almost surely, 2^21997263 is an apocalyptic number.

21997263 is a deficient number, since it is larger than the sum of its proper divisors (7332425).

21997263 is an equidigital number, since it uses as much as digits as its factorization.

21997263 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7332424.

The product of its digits is 40824, while the sum is 39.

The square root of 21997263 is about 4690.1239855680. The cubic root of 21997263 is about 280.1923126114.

The spelling of 21997263 in words is "twenty-one million, nine hundred ninety-seven thousand, two hundred sixty-three".