77728981 has 32 divisors (see below), whose sum is σ = 95800320. Its totient is φ = 62150400.

The previous prime is 77728967. The next prime is 77728991. The reversal of 77728981 is 18982777.

It is a cyclic number.

It is not a de Polignac number, because 77728981 - 2⁵ = 77728949 is a prime.

It is a super-2 number, since 2×77728981² = 12083588974596722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (77728921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 465360 + ... + 465526.

It is an arithmetic number, because the mean of its divisors is an integer number (2993760).

Almost surely, 2^77728981 is an apocalyptic number.

It is an amenable number.

77728981 is a deficient number, since it is larger than the sum of its proper divisors (18071339).

77728981 is a wasteful number, since it uses less digits than its factorization.

77728981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 345.

The product of its digits is 395136, while the sum is 49.

The square root of 77728981 is about 8816.4040855669. The cubic root of 77728981 is about 426.7704342202.

The spelling of 77728981 in words is "seventy-seven million, seven hundred twenty-eight thousand, nine hundred eighty-one".