21768641 has 2 divisors, whose sum is σ = 21768642. Its totient is φ = 21768640.

The previous prime is 21768611. The next prime is 21768667. The reversal of 21768641 is 14686712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18671041 + 3097600 = 4321^2 + 1760^2 .

It is a cyclic number.

It is not a de Polignac number, because 21768641 - 2¹⁰ = 21767617 is a prime.

It is not a weakly prime, because it can be changed into another prime (21768601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10884320 + 10884321.

It is an arithmetic number, because the mean of its divisors is an integer number (10884321).

Almost surely, 2^21768641 is an apocalyptic number.

It is an amenable number.

21768641 is a deficient number, since it is larger than the sum of its proper divisors (1).

21768641 is an equidigital number, since it uses as much as digits as its factorization.

21768641 is an evil number, because the sum of its binary digits is even.

The product of its digits is 16128, while the sum is 35.

The square root of 21768641 is about 4665.6876234913. The cubic root of 21768641 is about 279.2182317263.

The spelling of 21768641 in words is "twenty-one million, seven hundred sixty-eight thousand, six hundred forty-one".