19778641 has 2 divisors, whose sum is σ = 19778642. Its totient is φ = 19778640.

The previous prime is 19778617. The next prime is 19778657. The reversal of 19778641 is 14687791.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16524225 + 3254416 = 4065^2 + 1804^2 .

It is an emirp because it is prime and its reverse (14687791) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19778641 is a prime.

It is not a weakly prime, because it can be changed into another prime (19778611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9889320 + 9889321.

It is an arithmetic number, because the mean of its divisors is an integer number (9889321).

Almost surely, 2^19778641 is an apocalyptic number.

It is an amenable number.

19778641 is a deficient number, since it is larger than the sum of its proper divisors (1).

19778641 is an equidigital number, since it uses as much as digits as its factorization.

19778641 is an evil number, because the sum of its binary digits is even.

The product of its digits is 84672, while the sum is 43.

The square root of 19778641 is about 4447.3184055113. The cubic root of 19778641 is about 270.4366095481.

The spelling of 19778641 in words is "nineteen million, seven hundred seventy-eight thousand, six hundred forty-one".