21971737 has 2 divisors, whose sum is σ = 21971738. Its totient is φ = 21971736.

The previous prime is 21971723. The next prime is 21971749. The reversal of 21971737 is 73717912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19219456 + 2752281 = 4384^2 + 1659^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21971737 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21971696 and 21971705.

It is not a weakly prime, because it can be changed into another prime (21971707) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10985868 + 10985869.

It is an arithmetic number, because the mean of its divisors is an integer number (10985869).

Almost surely, 2^21971737 is an apocalyptic number.

It is an amenable number.

21971737 is a deficient number, since it is larger than the sum of its proper divisors (1).

21971737 is an equidigital number, since it uses as much as digits as its factorization.

21971737 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18522, while the sum is 37.

The square root of 21971737 is about 4687.4019456411. The cubic root of 21971737 is about 280.0838906794.

The spelling of 21971737 in words is "twenty-one million, nine hundred seventy-one thousand, seven hundred thirty-seven".