81523906 has 4 divisors (see below), whose sum is σ = 122285862. Its totient is φ = 40761952.

The previous prime is 81523879. The next prime is 81523909. The reversal of 81523906 is 60932518.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 59985025 + 21538881 = 7745^2 + 4641^2 .

It is a super-2 number, since 2×81523906² = 13292294498993672, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81523909) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20380975 + ... + 20380978.

Almost surely, 2^81523906 is an apocalyptic number.

81523906 is a deficient number, since it is larger than the sum of its proper divisors (40761956).

81523906 is a wasteful number, since it uses less digits than its factorization.

81523906 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40761955.

The product of its (nonzero) digits is 12960, while the sum is 34.

The square root of 81523906 is about 9029.0589764382. The cubic root of 81523906 is about 433.6057105462.

The spelling of 81523906 in words is "eighty-one million, five hundred twenty-three thousand, nine hundred six".