81221507 has 2 divisors, whose sum is σ = 81221508. Its totient is φ = 81221506.

The previous prime is 81221471. The next prime is 81221527. The reversal of 81221507 is 70512218.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81221507 - 2⁶ = 81221443 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81221527) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40610753 + 40610754.

It is an arithmetic number, because the mean of its divisors is an integer number (40610754).

Almost surely, 2^81221507 is an apocalyptic number.

81221507 is a deficient number, since it is larger than the sum of its proper divisors (1).

81221507 is an equidigital number, since it uses as much as digits as its factorization.

81221507 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1120, while the sum is 26.

The square root of 81221507 is about 9012.2975428023. The cubic root of 81221507 is about 433.0689175186.

The spelling of 81221507 in words is "eighty-one million, two hundred twenty-one thousand, five hundred seven".