820091861 has 4 divisors (see below), whose sum is σ = 837540672. Its totient is φ = 802643052.

The previous prime is 820091837. The next prime is 820091873. The reversal of 820091861 is 168190028.

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 820091861 - 2¹⁰ = 820090837 is a prime.

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 (820091561) 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, 8724335 + ... + 8724428.

It is an arithmetic number, because the mean of its divisors is an integer number (209385168).

Almost surely, 2^820091861 is an apocalyptic number.

It is an amenable number.

820091861 is a deficient number, since it is larger than the sum of its proper divisors (17448811).

820091861 is a wasteful number, since it uses less digits than its factorization.

820091861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17448810.

The product of its (nonzero) digits is 6912, while the sum is 35.

The square root of 820091861 is about 28637.2460442690. The cubic root of 820091861 is about 936.0251126319.

The spelling of 820091861 in words is "eight hundred twenty million, ninety-one thousand, eight hundred sixty-one".