1861540639 has 4 divisors (see below), whose sum is σ = 2127475024. Its totient is φ = 1595606256.

The previous prime is 1861540631. The next prime is 1861540651. The reversal of 1861540639 is 9360451681.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1861540639 - 2³ = 1861540631 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1861540595 and 1861540604.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1861540631) 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, 132967182 + ... + 132967195.

It is an arithmetic number, because the mean of its divisors is an integer number (531868756).

Almost surely, 2^1861540639 is an apocalyptic number.

1861540639 is a deficient number, since it is larger than the sum of its proper divisors (265934385).

1861540639 is an equidigital number, since it uses as much as digits as its factorization.

1861540639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 265934384.

The product of its (nonzero) digits is 155520, while the sum is 43.

The square root of 1861540639 is about 43145.5749642996. The cubic root of 1861540639 is about 1230.1484032278.

The spelling of 1861540639 in words is "one billion, eight hundred sixty-one million, five hundred forty thousand, six hundred thirty-nine".