381206221561 has 45 divisors (see below), whose sum is σ = 441410878139. Its totient is φ = 328960843200.

The previous prime is 381206221549. The next prime is 381206221577. The reversal of 381206221561 is 165122602183.

The square root of 381206221561 is 617419.

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

It can be written as a sum of positive squares in 7 ways, for example, as 68948781561 + 312257440000 = 262581^2 + 558800^2 .

It is not a de Polignac number, because 381206221561 - 2³⁷ = 243767268089 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (37).

It is a self number, because there is not a number n which added to its sum of digits gives 381206221561.

It is not an unprimeable number, because it can be changed into a prime (381206228561) 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 44 ways as a sum of consecutive naturals, for example, 9297712701 + ... + 9297712741.

Almost surely, 2^381206221561 is an apocalyptic number.

381206221561 is the 617419-th square number.

381206221561 is the 308710-th centered octagonal number.

It is an amenable number.

381206221561 is a deficient number, since it is larger than the sum of its proper divisors (60204656578).

381206221561 is an frugal number, since it uses more digits than its factorization.

381206221561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 252 (or 89 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 37.

It can be divided in two parts, 38120622 and 1561, that added together give a palindrome (38122183).

The spelling of 381206221561 in words is "three hundred eighty-one billion, two hundred six million, two hundred twenty-one thousand, five hundred sixty-one".