1861431821649 has 27 divisors (see below), whose sum is σ = 2699949372393. Its totient is φ = 1235800059912.

The previous prime is 1861431821609. The next prime is 1861431821657. The reversal of 1861431821649 is 9461281341681.

The square root of 1861431821649 is 1364343.

It is a perfect power (a square), and thus also a powerful number.

1861431821649 is a `hidden beast` number, since 1 + 8 + 614 + 3 + 1 + 8 + 2 + 16 + 4 + 9 = 666.

It is not a de Polignac number, because 1861431821649 - 2²³ = 1861423433041 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1861431821595 and 1861431821604.

It is not an unprimeable number, because it can be changed into a prime (1861431821609) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 1158326404 + ... + 1158328010.

Almost surely, 2^{1861431821649} is an apocalyptic number.

1861431821649 is the 1364343-rd square number.

1861431821649 is the 682172-nd centered octagonal number.

It is an amenable number.

1861431821649 is a deficient number, since it is larger than the sum of its proper divisors (838517550744).

1861431821649 is an frugal number, since it uses more digits than its factorization.

1861431821649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3786 (or 1893 counting only the distinct ones).

The product of its digits is 1990656, while the sum is 54.

The spelling of 1861431821649 in words is "one trillion, eight hundred sixty-one billion, four hundred thirty-one million, eight hundred twenty-one thousand, six hundred forty-nine".