19981257 has 4 divisors (see below), whose sum is σ = 26641680. Its totient is φ = 13320836.

The previous prime is 19981249. The next prime is 19981289. The reversal of 19981257 is 75218991.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 19981257 - 2³ = 19981249 is a prime.

It is not an unprimeable number, because it can be changed into a prime (19981207) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3330207 + ... + 3330212.

It is an arithmetic number, because the mean of its divisors is an integer number (6660420).

Almost surely, 2^19981257 is an apocalyptic number.

It is an amenable number.

19981257 is a deficient number, since it is larger than the sum of its proper divisors (6660423).

19981257 is an equidigital number, since it uses as much as digits as its factorization.

19981257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6660422.

The product of its digits is 45360, while the sum is 42.

The square root of 19981257 is about 4470.0399327075. The cubic root of 19981257 is about 271.3569412752.

The spelling of 19981257 in words is "nineteen million, nine hundred eighty-one thousand, two hundred fifty-seven".