81923890 has 32 divisors (see below), whose sum is σ = 149796864. Its totient is φ = 32256000.

The previous prime is 81923879. The next prime is 81923893. The reversal of 81923890 is 9832918.

It is not an unprimeable number, because it can be changed into a prime (81923893) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 318642 + ... + 318898.

It is an arithmetic number, because the mean of its divisors is an integer number (4681152).

Almost surely, 2^81923890 is an apocalyptic number.

81923890 is a deficient number, since it is larger than the sum of its proper divisors (67872974).

81923890 is a wasteful number, since it uses less digits than its factorization.

81923890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 642.

The product of its (nonzero) digits is 31104, while the sum is 40.

The square root of 81923890 is about 9051.1816908070. The cubic root of 81923890 is about 434.3136929504.

The spelling of 81923890 in words is "eighty-one million, nine hundred twenty-three thousand, eight hundred ninety".