1821908747961 has 27 divisors (see below), whose sum is σ = 2669654734383. Its totient is φ = 1197309738240.

The previous prime is 1821908747887. The next prime is 1821908747963. The reversal of 1821908747961 is 1697478091281.

The square root of 1821908747961 is 1349781.

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

1821908747961 is a `hidden beast` number, since 1 + 8 + 21 + 9 + 0 + 87 + 479 + 61 = 666.

It can be written as a sum of positive squares in only one way, i.e., 636301359225 + 1185607388736 = 797685^2 + 1088856^2 .

It is not a de Polignac number, because 1821908747961 - 2⁷ = 1821908747833 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1821908747963) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 287500185 + ... + 287506521.

Almost surely, 2^{1821908747961} is an apocalyptic number.

1821908747961 is the 1349781-st square number.

1821908747961 is the 674891-st centered octagonal number.

It is an amenable number.

1821908747961 is a deficient number, since it is larger than the sum of its proper divisors (847745986422).

1821908747961 is an frugal number, since it uses more digits than its factorization.

1821908747961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12822 (or 6411 counting only the distinct ones).

The product of its (nonzero) digits is 12192768, while the sum is 63.

The spelling of 1821908747961 in words is "one trillion, eight hundred twenty-one billion, nine hundred eight million, seven hundred forty-seven thousand, nine hundred sixty-one".