81643238 has 16 divisors (see below), whose sum is σ = 131245920. Its totient is φ = 37990656.

The previous prime is 81643229. The next prime is 81643241. The reversal of 81643238 is 83234618.

It is a happy number.

It is a super-2 number, since 2×81643238² = 13331236622249288, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 81643198 and 81643207.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 22283 + ... + 25686.

It is an arithmetic number, because the mean of its divisors is an integer number (8202870).

Almost surely, 2^81643238 is an apocalyptic number.

81643238 is a deficient number, since it is larger than the sum of its proper divisors (49602682).

81643238 is a wasteful number, since it uses less digits than its factorization.

81643238 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 48031.

The product of its digits is 27648, while the sum is 35.

The square root of 81643238 is about 9035.6647790852. The cubic root of 81643238 is about 433.8171733065.

The spelling of 81643238 in words is "eighty-one million, six hundred forty-three thousand, two hundred thirty-eight".