81605408 has 24 divisors (see below), whose sum is σ = 160866972. Its totient is φ = 40750336.

The previous prime is 81605393. The next prime is 81605413. The reversal of 81605408 is 80450618.

It can be written as a sum of positive squares in 2 ways, for example, as 77228944 + 4376464 = 8788^2 + 2092^2 .

It is a super-2 number, since 2×81605408² = 13318885229692928, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (32).

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, 39866 + ... + 41862.

Almost surely, 2^81605408 is an apocalyptic number.

It is an amenable number.

81605408 is a deficient number, since it is larger than the sum of its proper divisors (79261564).

81605408 is a wasteful number, since it uses less digits than its factorization.

81605408 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3284 (or 3276 counting only the distinct ones).

The product of its (nonzero) digits is 7680, while the sum is 32.

The square root of 81605408 is about 9033.5711653808. The cubic root of 81605408 is about 433.7501588197.

The spelling of 81605408 in words is "eighty-one million, six hundred five thousand, four hundred eight".