77081981 has 4 divisors (see below), whose sum is σ = 78536412. Its totient is φ = 75627552.

The previous prime is 77081951. The next prime is 77081987. The reversal of 77081981 is 18918077.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 68724100 + 8357881 = 8290^2 + 2891^2 .

It is a cyclic number.

It is not a de Polignac number, because 77081981 - 2¹⁰ = 77080957 is a prime.

It is a super-2 number, since 2×77081981² = 11883263589768722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (77081987) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 727136 + ... + 727241.

It is an arithmetic number, because the mean of its divisors is an integer number (19634103).

Almost surely, 2^77081981 is an apocalyptic number.

It is an amenable number.

77081981 is a deficient number, since it is larger than the sum of its proper divisors (1454431).

77081981 is a wasteful number, since it uses less digits than its factorization.

77081981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1454430.

The product of its (nonzero) digits is 28224, while the sum is 41.

The square root of 77081981 is about 8779.6344456931. The cubic root of 77081981 is about 425.5830171494.

The spelling of 77081981 in words is "seventy-seven million, eighty-one thousand, nine hundred eighty-one".