21787741 has 2 divisors, whose sum is σ = 21787742. Its totient is φ = 21787740.

The previous prime is 21787723. The next prime is 21787751. The reversal of 21787741 is 14778712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14791716 + 6996025 = 3846^2 + 2645^2 .

It is a cyclic number.

It is not a de Polignac number, because 21787741 - 2⁹ = 21787229 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21787741.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21787751) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10893870 + 10893871.

It is an arithmetic number, because the mean of its divisors is an integer number (10893871).

Almost surely, 2^21787741 is an apocalyptic number.

It is an amenable number.

21787741 is a deficient number, since it is larger than the sum of its proper divisors (1).

21787741 is an equidigital number, since it uses as much as digits as its factorization.

21787741 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 21952, while the sum is 37.

The square root of 21787741 is about 4667.7340326972. The cubic root of 21787741 is about 279.2998707106.

The spelling of 21787741 in words is "twenty-one million, seven hundred eighty-seven thousand, seven hundred forty-one".