81605650 has 24 divisors (see below), whose sum is σ = 173471040. Its totient is φ = 27978960.

The previous prime is 81605647. The next prime is 81605653. The reversal of 81605650 is 5650618.

It is an interprime number because it is at equal distance from previous prime (81605647) and next prime (81605653).

It is a super-2 number, since 2×81605650² = 13318964223845000, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81605653) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 116230 + ... + 116929.

It is an arithmetic number, because the mean of its divisors is an integer number (7227960).

Almost surely, 2^81605650 is an apocalyptic number.

81605650 is an abundant number, since it is smaller than the sum of its proper divisors (91865390).

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

81605650 is a wasteful number, since it uses less digits than its factorization.

81605650 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 233178 (or 233173 counting only the distinct ones).

The product of its (nonzero) digits is 7200, while the sum is 31.

The square root of 81605650 is about 9033.5845598522. The cubic root of 81605650 is about 433.7505875799.

The spelling of 81605650 in words is "eighty-one million, six hundred five thousand, six hundred fifty".