21971263 has 2 divisors, whose sum is σ = 21971264. Its totient is φ = 21971262.

The previous prime is 21971249. The next prime is 21971269. The reversal of 21971263 is 36217912.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21971263 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21971269) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10985631 + 10985632.

It is an arithmetic number, because the mean of its divisors is an integer number (10985632).

Almost surely, 2^21971263 is an apocalyptic number.

21971263 is a deficient number, since it is larger than the sum of its proper divisors (1).

21971263 is an equidigital number, since it uses as much as digits as its factorization.

21971263 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4536, while the sum is 31.

The square root of 21971263 is about 4687.3513843108. The cubic root of 21971263 is about 280.0818765658.

The spelling of 21971263 in words is "twenty-one million, nine hundred seventy-one thousand, two hundred sixty-three".