164901778561 has 9 divisors (see below), whose sum is σ = 178567997481. Its totient is φ = 152212153392.

The previous prime is 164901778553. The next prime is 164901778579. The reversal of 164901778561 is 165877109461.

The square root of 164901778561 is 406081.

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

It can be written as a sum of positive squares in 4 ways, for example, as 293060161 + 164608718400 = 17119^2 + 405720^2 .

It is not a de Polignac number, because 164901778561 - 2³ = 164901778553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (164901778961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 5263435 + ... + 5294671.

It is an arithmetic number, because the mean of its divisors is an integer number (19840888609).

Almost surely, 2^164901778561 is an apocalyptic number.

164901778561 is the 406081-st square number.

164901778561 is the 203041-st centered octagonal number.

It is an amenable number.

164901778561 is a deficient number, since it is larger than the sum of its proper divisors (13666218920).

164901778561 is an frugal number, since it uses more digits than its factorization.

164901778561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 62500 (or 31250 counting only the distinct ones).

The product of its (nonzero) digits is 2540160, while the sum is 55.

The spelling of 164901778561 in words is "one hundred sixty-four billion, nine hundred one million, seven hundred seventy-eight thousand, five hundred sixty-one".