81326251 has 4 divisors (see below), whose sum is σ = 85606600. Its totient is φ = 77045904.

The previous prime is 81326243. The next prime is 81326257. The reversal of 81326251 is 15262318.

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 81326251 - 2³ = 81326243 is a prime.

It is a super-2 number, since 2×81326251² = 13227918203430002, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81326257) 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, 2140146 + ... + 2140183.

It is an arithmetic number, because the mean of its divisors is an integer number (21401650).

Almost surely, 2^81326251 is an apocalyptic number.

81326251 is a deficient number, since it is larger than the sum of its proper divisors (4280349).

81326251 is a wasteful number, since it uses less digits than its factorization.

81326251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4280348.

The product of its digits is 2880, while the sum is 28.

The square root of 81326251 is about 9018.1068412389. The cubic root of 81326251 is about 433.2550007653.

Adding to 81326251 its reverse (15262318), we get a palindrome (96588569).

The spelling of 81326251 in words is "eighty-one million, three hundred twenty-six thousand, two hundred fifty-one".