19457981 has 4 divisors (see below), whose sum is σ = 19676700. Its totient is φ = 19239264.

The previous prime is 19457969. The next prime is 19457983. The reversal of 19457981 is 18975491.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18975491 = 157 ⋅120863.

It can be written as a sum of positive squares in 2 ways, for example, as 8791225 + 10666756 = 2965^2 + 3266^2 .

It is a cyclic number.

It is not a de Polignac number, because 19457981 - 2¹⁸ = 19195837 is a prime.

It is a super-2 number, since 2×19457981² = 757226049192722, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19457983) 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, 109226 + ... + 109403.

It is an arithmetic number, because the mean of its divisors is an integer number (4919175).

Almost surely, 2^19457981 is an apocalyptic number.

It is an amenable number.

19457981 is a deficient number, since it is larger than the sum of its proper divisors (218719).

19457981 is an equidigital number, since it uses as much as digits as its factorization.

19457981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 218718.

The product of its digits is 90720, while the sum is 44.

The square root of 19457981 is about 4411.1201525236. The cubic root of 19457981 is about 268.9671606240.

The spelling of 19457981 in words is "nineteen million, four hundred fifty-seven thousand, nine hundred eighty-one".