21395761 has 2 divisors, whose sum is σ = 21395762. Its totient is φ = 21395760.

The previous prime is 21395747. The next prime is 21395771. The reversal of 21395761 is 16759312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17172736 + 4223025 = 4144^2 + 2055^2 .

It is a cyclic number.

It is not a de Polignac number, because 21395761 - 2⁹ = 21395249 is a prime.

It is not a weakly prime, because it can be changed into another prime (21395771) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10697880 + 10697881.

It is an arithmetic number, because the mean of its divisors is an integer number (10697881).

Almost surely, 2^21395761 is an apocalyptic number.

It is an amenable number.

21395761 is a deficient number, since it is larger than the sum of its proper divisors (1).

21395761 is an equidigital number, since it uses as much as digits as its factorization.

21395761 is an evil number, because the sum of its binary digits is even.

The product of its digits is 11340, while the sum is 34.

The square root of 21395761 is about 4625.5552099180. Note that the first 3 decimals coincide. The cubic root of 21395761 is about 277.6147770747.

The spelling of 21395761 in words is "twenty-one million, three hundred ninety-five thousand, seven hundred sixty-one".