81225751 has 4 divisors (see below), whose sum is σ = 81361504. Its totient is φ = 81090000.

The previous prime is 81225737. The next prime is 81225757. The reversal of 81225751 is 15752218.

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

It is a cyclic number.

It is not a de Polignac number, because 81225751 - 2²³ = 72837143 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 (81225757) 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, 66975 + ... + 68176.

It is an arithmetic number, because the mean of its divisors is an integer number (20340376).

Almost surely, 2^81225751 is an apocalyptic number.

81225751 is a deficient number, since it is larger than the sum of its proper divisors (135753).

81225751 is a wasteful number, since it uses less digits than its factorization.

81225751 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 135752.

The product of its digits is 5600, while the sum is 31.

The square root of 81225751 is about 9012.5329957787. The cubic root of 81225751 is about 433.0764603174.

Adding to 81225751 its reverse (15752218), we get a palindrome (96977969).

The spelling of 81225751 in words is "eighty-one million, two hundred twenty-five thousand, seven hundred fifty-one".