81645970 has 64 divisors (see below), whose sum is σ = 174493440. Its totient is φ = 26926848.

The previous prime is 81645899. The next prime is 81645973. The reversal of 81645970 is 7954618.

It is not an unprimeable number, because it can be changed into a prime (81645973) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 218704 + ... + 219076.

It is an arithmetic number, because the mean of its divisors is an integer number (2726460).

Almost surely, 2^81645970 is an apocalyptic number.

81645970 is an abundant number, since it is smaller than the sum of its proper divisors (92847470).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81645970 is a wasteful number, since it uses less digits than its factorization.

81645970 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 499.

The product of its (nonzero) digits is 60480, while the sum is 40.

The square root of 81645970 is about 9035.8159565144. The cubic root of 81645970 is about 433.8220121449.

The spelling of 81645970 in words is "eighty-one million, six hundred forty-five thousand, nine hundred seventy".