81261251 has 2 divisors, whose sum is σ = 81261252. Its totient is φ = 81261250.

The previous prime is 81261239. The next prime is 81261281. The reversal of 81261251 is 15216218.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81261251 - 2²² = 77066947 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81261251.

It is not a weakly prime, because it can be changed into another prime (81261281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40630625 + 40630626.

It is an arithmetic number, because the mean of its divisors is an integer number (40630626).

Almost surely, 2^81261251 is an apocalyptic number.

81261251 is a deficient number, since it is larger than the sum of its proper divisors (1).

81261251 is an equidigital number, since it uses as much as digits as its factorization.

81261251 is an evil number, because the sum of its binary digits is even.

The product of its digits is 960, while the sum is 26.

The square root of 81261251 is about 9014.5022602471. The cubic root of 81261251 is about 433.1395436578.

Adding to 81261251 its reverse (15216218), we get a palindrome (96477469).

The spelling of 81261251 in words is "eighty-one million, two hundred sixty-one thousand, two hundred fifty-one".