81642556 has 6 divisors (see below), whose sum is σ = 142874480. Its totient is φ = 40821276.

The previous prime is 81642553. The next prime is 81642577. The reversal of 81642556 is 65524618.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81642553) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10205316 + ... + 10205323.

Almost surely, 2^81642556 is an apocalyptic number.

It is an amenable number.

81642556 is a deficient number, since it is larger than the sum of its proper divisors (61231924).

81642556 is a wasteful number, since it uses less digits than its factorization.

81642556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20410643 (or 20410641 counting only the distinct ones).

The product of its digits is 57600, while the sum is 37.

The square root of 81642556 is about 9035.6270396691. The cubic root of 81642556 is about 433.8159653513.

The spelling of 81642556 in words is "eighty-one million, six hundred forty-two thousand, five hundred fifty-six".