81279999 has 48 divisors (see below), whose sum is σ = 128366784. Its totient is φ = 49420800.

The previous prime is 81279983. The next prime is 81280037. The reversal of 81279999 is 99997218.

It is not a de Polignac number, because 81279999 - 2⁴ = 81279983 is a prime.

81279999 is a modest number, since divided by 9999 gives 8127 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81279959) 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, 517629 + ... + 517785.

It is an arithmetic number, because the mean of its divisors is an integer number (2674308).

Almost surely, 2^81279999 is an apocalyptic number.

81279999 is a deficient number, since it is larger than the sum of its proper divisors (47086785).

81279999 is a wasteful number, since it uses less digits than its factorization.

81279999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 288 (or 285 counting only the distinct ones).

The product of its digits is 734832, while the sum is 54.

The square root of 81279999 is about 9015.5420802079. The cubic root of 81279999 is about 433.1728513563.

The spelling of 81279999 in words is "eighty-one million, two hundred seventy-nine thousand, nine hundred ninety-nine".