81637461 has 6 divisors (see below), whose sum is σ = 117920790. Its totient is φ = 54424968.

The previous prime is 81637453. The next prime is 81637487. The reversal of 81637461 is 16473618.

It can be written as a sum of positive squares in only one way, i.e., 81270225 + 367236 = 9015^2 + 606^2 .

It is not a de Polignac number, because 81637461 - 2³ = 81637453 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81637421) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4535406 + ... + 4535423.

It is an arithmetic number, because the mean of its divisors is an integer number (19653465).

Almost surely, 2^81637461 is an apocalyptic number.

It is an amenable number.

81637461 is a deficient number, since it is larger than the sum of its proper divisors (36283329).

81637461 is a wasteful number, since it uses less digits than its factorization.

81637461 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9070835 (or 9070832 counting only the distinct ones).

The product of its digits is 24192, while the sum is 36.

The square root of 81637461 is about 9035.3450957891. The cubic root of 81637461 is about 433.8069408979.

The spelling of 81637461 in words is "eighty-one million, six hundred thirty-seven thousand, four hundred sixty-one".