15781131815642 has 4 divisors (see below), whose sum is σ = 23671697723466. Its totient is φ = 7890565907820.

The previous prime is 15781131815623. The next prime is 15781131815773. The reversal of 15781131815642 is 24651813118751.

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

It can be written as a sum of positive squares in only one way, i.e., 15700605835201 + 80525980441 = 3962399^2 + 283771^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3945282953909 + ... + 3945282953912.

Almost surely, 2^{15781131815642} is an apocalyptic number.

15781131815642 is a deficient number, since it is larger than the sum of its proper divisors (7890565907824).

15781131815642 is an equidigital number, since it uses as much as digits as its factorization.

15781131815642 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7890565907823.

The product of its digits is 1612800, while the sum is 53.

The spelling of 15781131815642 in words is "fifteen trillion, seven hundred eighty-one billion, one hundred thirty-one million, eight hundred fifteen thousand, six hundred forty-two".