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81649521 = 32175310069
BaseRepresentation
bin1001101110111…
…01111101110001
312200122020002100
410313131331301
5131400241041
612034011013
72011003152
oct467357561
9180566070
1081649521
11420a8548
1223416a69
1313bba135
14abb5929
15727c6b6
hex4dddf71

81649521 has 24 divisors (see below), whose sum is σ = 127244520. Its totient is φ = 50259456.

The previous prime is 81649489. The next prime is 81649559. The reversal of 81649521 is 12594618.

81649521 is a `hidden beast` number, since 8 + 1 + 649 + 5 + 2 + 1 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 20575296 + 61074225 = 4536^2 + 7815^2 .

It is not a de Polignac number, because 81649521 - 25 = 81649489 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81649571) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3075 + ... + 13143.

It is an arithmetic number, because the mean of its divisors is an integer number (5301855).

Almost surely, 281649521 is an apocalyptic number.

It is an amenable number.

81649521 is a deficient number, since it is larger than the sum of its proper divisors (45594999).

81649521 is a wasteful number, since it uses less digits than its factorization.

81649521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10145 (or 10142 counting only the distinct ones).

The product of its digits is 17280, while the sum is 36.

The square root of 81649521 is about 9036.0124501906. The cubic root of 81649521 is about 433.8283014108.

The spelling of 81649521 in words is "eighty-one million, six hundred forty-nine thousand, five hundred twenty-one".

Divisors: 1 3 9 17 51 53 153 159 477 901 2703 8109 10069 30207 90621 171173 513519 533657 1540557 1600971 4802913 9072169 27216507 81649521