81561525 has 12 divisors (see below), whose sum is σ = 134848512. Its totient is φ = 43499440.

The previous prime is 81561523. The next prime is 81561551. The reversal of 81561525 is 52516518.

It is not a de Polignac number, because 81561525 - 2¹ = 81561523 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81561521) 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, 543669 + ... + 543818.

It is an arithmetic number, because the mean of its divisors is an integer number (11237376).

Almost surely, 2^81561525 is an apocalyptic number.

It is an amenable number.

81561525 is a deficient number, since it is larger than the sum of its proper divisors (53286987).

81561525 is a wasteful number, since it uses less digits than its factorization.

81561525 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1087500 (or 1087495 counting only the distinct ones).

The product of its digits is 12000, while the sum is 33.

The square root of 81561525 is about 9031.1419543710. The cubic root of 81561525 is about 433.6723957091.

The spelling of 81561525 in words is "eighty-one million, five hundred sixty-one thousand, five hundred twenty-five".