81621567 has 16 divisors (see below), whose sum is σ = 121104480. Its totient is φ = 54331776.

The previous prime is 81621559. The next prime is 81621581. The reversal of 81621567 is 76512618.

It is not a de Polignac number, because 81621567 - 2³ = 81621559 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81621517) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19623 + ... + 23415.

It is an arithmetic number, because the mean of its divisors is an integer number (7569030).

Almost surely, 2^81621567 is an apocalyptic number.

81621567 is a deficient number, since it is larger than the sum of its proper divisors (39482913).

81621567 is a wasteful number, since it uses less digits than its factorization.

81621567 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4599 (or 4593 counting only the distinct ones).

The product of its digits is 20160, while the sum is 36.

The square root of 81621567 is about 9034.4655071565. The cubic root of 81621567 is about 433.7787864414.

The spelling of 81621567 in words is "eighty-one million, six hundred twenty-one thousand, five hundred sixty-seven".