19875661 has 4 divisors (see below), whose sum is σ = 21404572. Its totient is φ = 18346752.

The previous prime is 19875659. The next prime is 19875673. The reversal of 19875661 is 16657891.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 16657891 = 1619 ⋅10289.

It can be written as a sum of positive squares in 2 ways, for example, as 1334025 + 18541636 = 1155^2 + 4306^2 .

It is a cyclic number.

It is not a de Polignac number, because 19875661 - 2¹ = 19875659 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19875161) 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, 764436 + ... + 764461.

It is an arithmetic number, because the mean of its divisors is an integer number (5351143).

Almost surely, 2^19875661 is an apocalyptic number.

It is an amenable number.

19875661 is a deficient number, since it is larger than the sum of its proper divisors (1528911).

19875661 is a wasteful number, since it uses less digits than its factorization.

19875661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1528910.

The product of its digits is 90720, while the sum is 43.

The square root of 19875661 is about 4458.2127584941. The cubic root of 19875661 is about 270.8780786242.

The spelling of 19875661 in words is "nineteen million, eight hundred seventy-five thousand, six hundred sixty-one".