21971749 has 2 divisors, whose sum is σ = 21971750. Its totient is φ = 21971748.

The previous prime is 21971737. The next prime is 21971783. The reversal of 21971749 is 94717912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21921124 + 50625 = 4682^2 + 225^2 .

It is a cyclic number.

It is not a de Polignac number, because 21971749 - 2²¹ = 19874597 is a prime.

It is a Chen prime.

It is a plaindrome in base 11.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21971149) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10985874 + 10985875.

It is an arithmetic number, because the mean of its divisors is an integer number (10985875).

Almost surely, 2^21971749 is an apocalyptic number.

It is an amenable number.

21971749 is a deficient number, since it is larger than the sum of its proper divisors (1).

21971749 is an equidigital number, since it uses as much as digits as its factorization.

21971749 is an evil number, because the sum of its binary digits is even.

The product of its digits is 31752, while the sum is 40.

The square root of 21971749 is about 4687.4032256677. The cubic root of 21971749 is about 280.0839416692.

The spelling of 21971749 in words is "twenty-one million, nine hundred seventy-one thousand, seven hundred forty-nine".