81256501 has 2 divisors, whose sum is σ = 81256502. Its totient is φ = 81256500.

The previous prime is 81256499. The next prime is 81256507. The reversal of 81256501 is 10565218.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 63202500 + 18054001 = 7950^2 + 4249^2 .

It is a cyclic number.

It is not a de Polignac number, because 81256501 - 2¹ = 81256499 is a prime.

Together with 81256499, it forms a pair of twin primes.

It is an alternating number because its digits alternate between even and odd.

It is a self number, because there is not a number n which added to its sum of digits gives 81256501.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81256507) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40628250 + 40628251.

It is an arithmetic number, because the mean of its divisors is an integer number (40628251).

Almost surely, 2^81256501 is an apocalyptic number.

It is an amenable number.

81256501 is a deficient number, since it is larger than the sum of its proper divisors (1).

81256501 is an equidigital number, since it uses as much as digits as its factorization.

81256501 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2400, while the sum is 28.

The square root of 81256501 is about 9014.2387920445. The cubic root of 81256501 is about 433.1311039940.

The spelling of 81256501 in words is "eighty-one million, two hundred fifty-six thousand, five hundred one".