81277780821 has 8 divisors (see below), whose sum is σ = 108377431200. Its totient is φ = 54181658832.

The previous prime is 81277780819. The next prime is 81277780849. The reversal of 81277780821 is 12808777218.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81277780821 - 2¹ = 81277780819 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81277780891) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 827871 + ... + 920828.

It is an arithmetic number, because the mean of its divisors is an integer number (13547178900).

Almost surely, 2^81277780821 is an apocalyptic number.

It is an amenable number.

81277780821 is a deficient number, since it is larger than the sum of its proper divisors (27099650379).

81277780821 is a wasteful number, since it uses less digits than its factorization.

81277780821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1764195.

The product of its (nonzero) digits is 702464, while the sum is 51.

The spelling of 81277780821 in words is "eighty-one billion, two hundred seventy-seven million, seven hundred eighty thousand, eight hundred twenty-one".