1897778561 has 16 divisors (see below), whose sum is σ = 2299614336. Its totient is φ = 1528886016.

The previous prime is 1897778513. The next prime is 1897778569. The reversal of 1897778561 is 1658777981.

It is not a de Polignac number, because 1897778561 - 2²⁶ = 1830669697 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1897778561.

It is not an unprimeable number, because it can be changed into a prime (1897778569) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 79550 + ... + 100616.

It is an arithmetic number, because the mean of its divisors is an integer number (143725896).

Almost surely, 2^1897778561 is an apocalyptic number.

It is an amenable number.

1897778561 is a deficient number, since it is larger than the sum of its proper divisors (401835775).

1897778561 is a wasteful number, since it uses less digits than its factorization.

1897778561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21848.

The product of its digits is 5927040, while the sum is 59.

The square root of 1897778561 is about 43563.5003299781. The cubic root of 1897778561 is about 1238.0794412707.

The spelling of 1897778561 in words is "one billion, eight hundred ninety-seven million, seven hundred seventy-eight thousand, five hundred sixty-one".