81921859 has 8 divisors (see below), whose sum is σ = 83511648. Its totient is φ = 80344320.

The previous prime is 81921857. The next prime is 81921881. The reversal of 81921859 is 95812918.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81921859 - 2¹ = 81921857 is a prime.

It is a super-2 number, since 2×81921859² = 13422381964031762, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81921857) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11059 + ... + 16915.

It is an arithmetic number, because the mean of its divisors is an integer number (10438956).

Almost surely, 2^81921859 is an apocalyptic number.

81921859 is a deficient number, since it is larger than the sum of its proper divisors (1589789).

81921859 is a wasteful number, since it uses less digits than its factorization.

81921859 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6125.

The product of its digits is 51840, while the sum is 43.

The square root of 81921859 is about 9051.0694948166. The cubic root of 81921859 is about 434.3101038532.

The spelling of 81921859 in words is "eighty-one million, nine hundred twenty-one thousand, eight hundred fifty-nine".