81428505 has 16 divisors (see below), whose sum is σ = 131042880. Its totient is φ = 43176128.

The previous prime is 81428497. The next prime is 81428513. The reversal of 81428505 is 50582418.

It is an interprime number because it is at equal distance from previous prime (81428497) and next prime (81428513).

It is a cyclic number.

It is not a de Polignac number, because 81428505 - 2³ = 81428497 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13095 + ... + 18284.

It is an arithmetic number, because the mean of its divisors is an integer number (8190180).

Almost surely, 2^81428505 is an apocalyptic number.

It is an amenable number.

81428505 is a deficient number, since it is larger than the sum of its proper divisors (49614375).

81428505 is a wasteful number, since it uses less digits than its factorization.

81428505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31560.

The product of its (nonzero) digits is 12800, while the sum is 33.

The square root of 81428505 is about 9023.7744320212. The cubic root of 81428505 is about 433.4365063342.

The spelling of 81428505 in words is "eighty-one million, four hundred twenty-eight thousand, five hundred five".