21971493 has 10 divisors (see below), whose sum is σ = 32821734. Its totient is φ = 14647608.

The previous prime is 21971489. The next prime is 21971501. The reversal of 21971493 is 39417912.

It can be written as a sum of positive squares in only one way, i.e., 18122049 + 3849444 = 4257^2 + 1962^2 .

It is not a de Polignac number, because 21971493 - 2² = 21971489 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21971413) 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 9 ways as a sum of consecutive naturals, for example, 135546 + ... + 135707.

Almost surely, 2^21971493 is an apocalyptic number.

It is an amenable number.

21971493 is a deficient number, since it is larger than the sum of its proper divisors (10850241).

21971493 is an equidigital number, since it uses as much as digits as its factorization.

21971493 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 271265 (or 271256 counting only the distinct ones).

The product of its digits is 13608, while the sum is 36.

The square root of 21971493 is about 4687.3759183577. The cubic root of 21971493 is about 280.0828538819.

It can be divided in two parts, 219714 and 93, that multiplied together give a palindrome (20433402).

The spelling of 21971493 in words is "twenty-one million, nine hundred seventy-one thousand, four hundred ninety-three".