81397778 has 32 divisors (see below), whose sum is σ = 152661888. Its totient is φ = 31622400.

The previous prime is 81397777. The next prime is 81397781. The reversal of 81397778 is 87779318.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81397777) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 82826 + ... + 83802.

It is an arithmetic number, because the mean of its divisors is an integer number (4770684).

Almost surely, 2^81397778 is an apocalyptic number.

81397778 is a deficient number, since it is larger than the sum of its proper divisors (71264110).

81397778 is a wasteful number, since it uses less digits than its factorization.

81397778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1538.

The product of its digits is 592704, while the sum is 50.

The square root of 81397778 is about 9022.0717133040. The cubic root of 81397778 is about 433.3819804688.

The spelling of 81397778 in words is "eighty-one million, three hundred ninety-seven thousand, seven hundred seventy-eight".