81671251 has 4 divisors (see below), whose sum is σ = 83212272. Its totient is φ = 80130232.

The previous prime is 81671209. The next prime is 81671263. The reversal of 81671251 is 15217618.

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 81671251 - 2⁷ = 81671123 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81671201) 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, 770431 + ... + 770536.

It is an arithmetic number, because the mean of its divisors is an integer number (20803068).

Almost surely, 2^81671251 is an apocalyptic number.

81671251 is a deficient number, since it is larger than the sum of its proper divisors (1541021).

81671251 is a wasteful number, since it uses less digits than its factorization.

81671251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1541020.

The product of its digits is 3360, while the sum is 31.

The square root of 81671251 is about 9037.2147811148. The cubic root of 81671251 is about 433.8667839913.

Adding to 81671251 its reverse (15217618), we get a palindrome (96888869).

The spelling of 81671251 in words is "eighty-one million, six hundred seventy-one thousand, two hundred fifty-one".