1861016021 has 4 divisors (see below), whose sum is σ = 1866887052. Its totient is φ = 1855144992.

The previous prime is 1861015967. The next prime is 1861016023. The reversal of 1861016021 is 1206101681.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1206101681 = 12473 ⋅96697.

It can be written as a sum of positive squares in 2 ways, for example, as 198415396 + 1662600625 = 14086^2 + 40775^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1861016021 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 (1861016023) 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, 2935040 + ... + 2935673.

It is an arithmetic number, because the mean of its divisors is an integer number (466721763).

Almost surely, 2^1861016021 is an apocalyptic number.

It is an amenable number.

1861016021 is a deficient number, since it is larger than the sum of its proper divisors (5871031).

1861016021 is an equidigital number, since it uses as much as digits as its factorization.

1861016021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5871030.

The product of its (nonzero) digits is 576, while the sum is 26.

The square root of 1861016021 is about 43139.4949089578. The cubic root of 1861016021 is about 1230.0328325340.

The spelling of 1861016021 in words is "one billion, eight hundred sixty-one million, sixteen thousand, twenty-one".