19961639 has 2 divisors, whose sum is σ = 19961640. Its totient is φ = 19961638.

The previous prime is 19961633. The next prime is 19961653. The reversal of 19961639 is 93616991.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19961639 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 19961639.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19961633) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9980819 + 9980820.

It is an arithmetic number, because the mean of its divisors is an integer number (9980820).

Almost surely, 2^19961639 is an apocalyptic number.

19961639 is a deficient number, since it is larger than the sum of its proper divisors (1).

19961639 is an equidigital number, since it uses as much as digits as its factorization.

19961639 is an evil number, because the sum of its binary digits is even.

The product of its digits is 78732, while the sum is 44.

The square root of 19961639 is about 4467.8450062642. The cubic root of 19961639 is about 271.2681042940.

The spelling of 19961639 in words is "nineteen million, nine hundred sixty-one thousand, six hundred thirty-nine".