81857989 has 12 divisors (see below), whose sum is σ = 86037952. Its totient is φ = 77873400.

The previous prime is 81857899. The next prime is 81858013. The reversal of 81857989 is 98975818.

It is not a de Polignac number, because 81857989 - 2¹³ = 81849797 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81855989) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 143074 + ... + 143644.

Almost surely, 2^81857989 is an apocalyptic number.

It is an amenable number.

81857989 is a deficient number, since it is larger than the sum of its proper divisors (4179963).

81857989 is a wasteful number, since it uses less digits than its factorization.

81857989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 888 (or 865 counting only the distinct ones).

The product of its digits is 1451520, while the sum is 55.

The square root of 81857989 is about 9047.5404945211. The cubic root of 81857989 is about 434.1972052172.

The spelling of 81857989 in words is "eighty-one million, eight hundred fifty-seven thousand, nine hundred eighty-nine".