81421251 has 16 divisors (see below), whose sum is σ = 115415040. Its totient is φ = 50911200.

The previous prime is 81421247. The next prime is 81421253. The reversal of 81421251 is 15212418.

It is not a de Polignac number, because 81421251 - 2² = 81421247 is a prime.

It is a super-2 number, since 2×81421251² = 13258840228810002, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81421253) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1315 + ... + 12828.

It is an arithmetic number, because the mean of its divisors is an integer number (7213440).

Almost surely, 2^81421251 is an apocalyptic number.

81421251 is a deficient number, since it is larger than the sum of its proper divisors (33993789).

81421251 is a wasteful number, since it uses less digits than its factorization.

81421251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14266.

The product of its digits is 640, while the sum is 24.

The square root of 81421251 is about 9023.3724848307. The cubic root of 81421251 is about 433.4236351584.

Adding to 81421251 its reverse (15212418), we get a palindrome (96633669).

The spelling of 81421251 in words is "eighty-one million, four hundred twenty-one thousand, two hundred fifty-one".