81553111 has 4 divisors (see below), whose sum is σ = 85845400. Its totient is φ = 77260824.

The previous prime is 81553099. The next prime is 81553123. The reversal of 81553111 is 11135518.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (81553099) and next prime (81553123).

It is a cyclic number.

It is not a de Polignac number, because 81553111 - 2¹³ = 81544919 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81553151) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2146116 + ... + 2146153.

It is an arithmetic number, because the mean of its divisors is an integer number (21461350).

Almost surely, 2^81553111 is an apocalyptic number.

81553111 is a deficient number, since it is larger than the sum of its proper divisors (4292289).

81553111 is a wasteful number, since it uses less digits than its factorization.

81553111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4292288.

The product of its digits is 600, while the sum is 25.

The square root of 81553111 is about 9030.6761097938. The cubic root of 81553111 is about 433.6574824478.

Adding to 81553111 its reverse (11135518), we get a palindrome (92688629).

The spelling of 81553111 in words is "eighty-one million, five hundred fifty-three thousand, one hundred eleven".