81378402361 has 27 divisors (see below), whose sum is σ = 86713190991. Its totient is φ = 76365370224.

The previous prime is 81378402353. The next prime is 81378402379. The reversal of 81378402361 is 16320487318.

The square root of 81378402361 is 285269.

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

It can be written as a sum of positive squares in only one way, i.e., 23853258025 + 57525144336 = 154445^2 + 239844^2 .

It is not a de Polignac number, because 81378402361 - 2³ = 81378402353 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81378402341) 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, 518333695 + ... + 518333851.

Almost surely, 2^81378402361 is an apocalyptic number.

81378402361 is the 285269-th square number.

81378402361 is the 142635-th centered octagonal number.

It is an amenable number.

81378402361 is a deficient number, since it is larger than the sum of its proper divisors (5334788630).

81378402361 is an frugal number, since it uses more digits than its factorization.

81378402361 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 518 (or 259 counting only the distinct ones).

The product of its (nonzero) digits is 193536, while the sum is 43.

Adding to 81378402361 its reverse (16320487318), we get a palindrome (97698889679).

The spelling of 81378402361 in words is "eighty-one billion, three hundred seventy-eight million, four hundred two thousand, three hundred sixty-one".