19979581 has 2 divisors, whose sum is σ = 19979582. Its totient is φ = 19979580.

The previous prime is 19979567. The next prime is 19979611. The reversal of 19979581 is 18597991.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19660356 + 319225 = 4434^2 + 565^2 .

It is a cyclic number.

It is not a de Polignac number, because 19979581 - 2⁵ = 19979549 is a prime.

It is a super-2 number, since 2×19979581² = 798367313871122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19979081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9989790 + 9989791.

It is an arithmetic number, because the mean of its divisors is an integer number (9989791).

Almost surely, 2^19979581 is an apocalyptic number.

It is an amenable number.

19979581 is a deficient number, since it is larger than the sum of its proper divisors (1).

19979581 is an equidigital number, since it uses as much as digits as its factorization.

19979581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 204120, while the sum is 49.

The square root of 19979581 is about 4469.8524584152. The cubic root of 19979581 is about 271.3493540490.

The spelling of 19979581 in words is "nineteen million, nine hundred seventy-nine thousand, five hundred eighty-one".