19999861 has 4 divisors (see below), whose sum is σ = 22856992. Its totient is φ = 17142732.

The previous prime is 19999843. The next prime is 19999873. The reversal of 19999861 is 16899991.

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, and also an emirpimes, since its reverse is a distinct semiprime: 16899991 = 31 ⋅545161.

It is a cyclic number.

It is not a de Polignac number, because 19999861 - 2²³ = 11611253 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 19999799 and 19999808.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19999831) 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, 1428555 + ... + 1428568.

It is an arithmetic number, because the mean of its divisors is an integer number (5714248).

Almost surely, 2^19999861 is an apocalyptic number.

It is an amenable number.

19999861 is a deficient number, since it is larger than the sum of its proper divisors (2857131).

19999861 is an equidigital number, since it uses as much as digits as its factorization.

19999861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2857130.

The product of its digits is 314928, while the sum is 52.

The square root of 19999861 is about 4472.1204143001. The cubic root of 19999861 is about 271.4411328180.

The spelling of 19999861 in words is "nineteen million, nine hundred ninety-nine thousand, eight hundred sixty-one".