19881557 has 2 divisors, whose sum is σ = 19881558. Its totient is φ = 19881556.

The previous prime is 19881541. The next prime is 19881607. The reversal of 19881557 is 75518891.

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., 19483396 + 398161 = 4414^2 + 631^2 .

It is a cyclic number.

It is not a de Polignac number, because 19881557 - 2⁴ = 19881541 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19881457) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9940778 + 9940779.

It is an arithmetic number, because the mean of its divisors is an integer number (9940779).

Almost surely, 2^19881557 is an apocalyptic number.

It is an amenable number.

19881557 is a deficient number, since it is larger than the sum of its proper divisors (1).

19881557 is an equidigital number, since it uses as much as digits as its factorization.

19881557 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 100800, while the sum is 44.

The square root of 19881557 is about 4458.8739609906. The cubic root of 19881557 is about 270.9048607817.

The spelling of 19881557 in words is "nineteen million, eight hundred eighty-one thousand, five hundred fifty-seven".