81639587 has 2 divisors, whose sum is σ = 81639588. Its totient is φ = 81639586.

The previous prime is 81639527. The next prime is 81639601. The reversal of 81639587 is 78593618.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81639587 - 2¹⁰ = 81638563 is a prime.

It is not a weakly prime, because it can be changed into another prime (81639527) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40819793 + 40819794.

It is an arithmetic number, because the mean of its divisors is an integer number (40819794).

Almost surely, 2^81639587 is an apocalyptic number.

81639587 is a deficient number, since it is larger than the sum of its proper divisors (1).

81639587 is an equidigital number, since it uses as much as digits as its factorization.

81639587 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 362880, while the sum is 47.

The square root of 81639587 is about 9035.4627440989. The cubic root of 81639587 is about 433.8107065938.

The spelling of 81639587 in words is "eighty-one million, six hundred thirty-nine thousand, five hundred eighty-seven".