21905071 has 2 divisors, whose sum is σ = 21905072. Its totient is φ = 21905070.

The previous prime is 21905053. The next prime is 21905077. The reversal of 21905071 is 17050912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21905071 - 2⁷ = 21904943 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21905077) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10952535 + 10952536.

It is an arithmetic number, because the mean of its divisors is an integer number (10952536).

Almost surely, 2^21905071 is an apocalyptic number.

21905071 is a deficient number, since it is larger than the sum of its proper divisors (1).

21905071 is an equidigital number, since it uses as much as digits as its factorization.

21905071 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 630, while the sum is 25.

The square root of 21905071 is about 4680.2853545484. The cubic root of 21905071 is about 279.8003295859.

Adding to 21905071 its reverse (17050912), we get a palindrome (38955983).

The spelling of 21905071 in words is "twenty-one million, nine hundred five thousand, seventy-one".