20191861 has 4 divisors (see below), whose sum is σ = 21069792. Its totient is φ = 19313932.

The previous prime is 20191849. The next prime is 20191867. The reversal of 20191861 is 16819102.

It is a happy number.

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 a de Polignac number, because none of the positive numbers 2^k-20191861 is a prime.

It is a super-2 number, since 2×20191861² = 815422501286642, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20191867) 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, 438931 + ... + 438976.

It is an arithmetic number, because the mean of its divisors is an integer number (5267448).

Almost surely, 2^20191861 is an apocalyptic number.

It is an amenable number.

20191861 is a deficient number, since it is larger than the sum of its proper divisors (877931).

20191861 is an equidigital number, since it uses as much as digits as its factorization.

20191861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 877930.

The product of its (nonzero) digits is 864, while the sum is 28.

The square root of 20191861 is about 4493.5354677581. The cubic root of 20191861 is about 272.3069856144.

The spelling of 20191861 in words is "twenty million, one hundred ninety-one thousand, eight hundred sixty-one".