19781213 has 2 divisors, whose sum is σ = 19781214. Its totient is φ = 19781212.

The previous prime is 19781207. The next prime is 19781221. The reversal of 19781213 is 31218791.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12694969 + 7086244 = 3563^2 + 2662^2 .

It is a cyclic number.

It is not a de Polignac number, because 19781213 - 2¹² = 19777117 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 19781213.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19781513) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9890606 + 9890607.

It is an arithmetic number, because the mean of its divisors is an integer number (9890607).

Almost surely, 2^19781213 is an apocalyptic number.

It is an amenable number.

19781213 is a deficient number, since it is larger than the sum of its proper divisors (1).

19781213 is an equidigital number, since it uses as much as digits as its factorization.

19781213 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3024, while the sum is 32.

The square root of 19781213 is about 4447.6075591266. The cubic root of 19781213 is about 270.4483314996.

The spelling of 19781213 in words is "nineteen million, seven hundred eighty-one thousand, two hundred thirteen".