81533420 has 24 divisors (see below), whose sum is σ = 175398048. Its totient is φ = 31817600.

The previous prime is 81533407. The next prime is 81533437. The reversal of 81533420 is 2433518.

It is a self number, because there is not a number n which added to its sum of digits gives 81533420.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 48896 + ... + 50535.

It is an arithmetic number, because the mean of its divisors is an integer number (7308252).

Almost surely, 2^81533420 is an apocalyptic number.

It is an amenable number.

81533420 is an abundant number, since it is smaller than the sum of its proper divisors (93864628).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81533420 is a wasteful number, since it uses less digits than its factorization.

81533420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 99481 (or 99479 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 26.

The square root of 81533420 is about 9029.5858155289. The cubic root of 81533420 is about 433.6225774362.

Adding to 81533420 its reverse (2433518), we get a palindrome (83966938).

The spelling of 81533420 in words is "eighty-one million, five hundred thirty-three thousand, four hundred twenty".