81620810 has 8 divisors (see below), whose sum is σ = 146917476. Its totient is φ = 32648320.

The previous prime is 81620809. The next prime is 81620831. The reversal of 81620810 is 1802618.

It can be written as a sum of positive squares in 2 ways, for example, as 81522841 + 97969 = 9029^2 + 313^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×81620810² = 13323913250112200, which contains 22 as substring.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 81620810.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4081031 + ... + 4081050.

Almost surely, 2^81620810 is an apocalyptic number.

81620810 is a deficient number, since it is larger than the sum of its proper divisors (65296666).

81620810 is a wasteful number, since it uses less digits than its factorization.

81620810 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8162088.

The product of its (nonzero) digits is 768, while the sum is 26.

The square root of 81620810 is about 9034.4236119412. The cubic root of 81620810 is about 433.7774454088. Note that the first 3 decimals are identical.

The spelling of 81620810 in words is "eighty-one million, six hundred twenty thousand, eight hundred ten".