81533519 has 4 divisors (see below), whose sum is σ = 81552744. Its totient is φ = 81514296.

The previous prime is 81533509. The next prime is 81533521. The reversal of 81533519 is 91533518.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81533519 is a prime.

It is a super-2 number, since 2×81533519² = 13295429441046722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81533509) 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, 137 + ... + 12770.

It is an arithmetic number, because the mean of its divisors is an integer number (20388186).

Almost surely, 2^81533519 is an apocalyptic number.

81533519 is a deficient number, since it is larger than the sum of its proper divisors (19225).

81533519 is a wasteful number, since it uses less digits than its factorization.

81533519 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19224.

The product of its digits is 16200, while the sum is 35.

The square root of 81533519 is about 9029.5912975062. The cubic root of 81533519 is about 433.6227529414.

Subtracting 81533519 from its reverse (91533518), we obtain a palindrome (9999999).

The spelling of 81533519 in words is "eighty-one million, five hundred thirty-three thousand, five hundred nineteen".