81777729 has 48 divisors (see below), whose sum is σ = 128701440. Its totient is φ = 46015200.

The previous prime is 81777727. The next prime is 81777743. The reversal of 81777729 is 92777718.

It is not a de Polignac number, because 81777729 - 2¹ = 81777727 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81777727) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 489604 + ... + 489770.

It is an arithmetic number, because the mean of its divisors is an integer number (2681280).

Almost surely, 2^81777729 is an apocalyptic number.

It is an amenable number.

81777729 is a deficient number, since it is larger than the sum of its proper divisors (46923711).

81777729 is a wasteful number, since it uses less digits than its factorization.

81777729 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 282 (or 271 counting only the distinct ones).

The product of its digits is 345744, while the sum is 48.

The square root of 81777729 is about 9043.1039472075. The cubic root of 81777729 is about 434.0552518018.

The spelling of 81777729 in words is "eighty-one million, seven hundred seventy-seven thousand, seven hundred twenty-nine".