77281681 has 9 divisors (see below), whose sum is σ = 79144891. Its totient is φ = 75461944.

The previous prime is 77281661. The next prime is 77281691. The reversal of 77281681 is 18618277.

The square root of 77281681 is 8791.

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., 9054081 + 68227600 = 3009^2 + 8260^2 .

It is not a de Polignac number, because 77281681 - 2¹¹ = 77279633 is a prime.

It is a super-2 number, since 2×77281681² = 11944916436371522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (77281601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 518595 + ... + 518743.

Almost surely, 2^77281681 is an apocalyptic number.

77281681 is the 8791-st square number.

77281681 is the 4396-th centered octagonal number.

It is an amenable number.

77281681 is a deficient number, since it is larger than the sum of its proper divisors (1863210).

77281681 is an frugal number, since it uses more digits than its factorization.

77281681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 416 (or 208 counting only the distinct ones).

The product of its digits is 37632, while the sum is 40.

The cubic root of 77281681 is about 425.9502263550.

It can be divided in two parts, 7728 and 1681, that added together give a square (9409 = 97²).

The spelling of 77281681 in words is "seventy-seven million, two hundred eighty-one thousand, six hundred eighty-one".