81780111 has 40 divisors (see below), whose sum is σ = 145711104. Its totient is φ = 44692560.

The previous prime is 81780107. The next prime is 81780119. The reversal of 81780111 is 11108718.

It is not a de Polignac number, because 81780111 - 2² = 81780107 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81780119) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 9906 + ... + 16176.

Almost surely, 2^81780111 is an apocalyptic number.

81780111 is a gapful number since it is divisible by the number (81) formed by its first and last digit.

81780111 is a deficient number, since it is larger than the sum of its proper divisors (63930993).

81780111 is a wasteful number, since it uses less digits than its factorization.

81780111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6313 (or 6304 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 27.

The square root of 81780111 is about 9043.2356488151. The cubic root of 81780111 is about 434.0594661096.

Adding to 81780111 its reverse (11108718), we get a palindrome (92888829).

The spelling of 81780111 in words is "eighty-one million, seven hundred eighty thousand, one hundred eleven".