81637761 has 4 divisors (see below), whose sum is σ = 108850352. Its totient is φ = 54425172.

The previous prime is 81637753. The next prime is 81637781. The reversal of 81637761 is 16773618.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 81637761 - 2³ = 81637753 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81637781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13606291 + ... + 13606296.

It is an arithmetic number, because the mean of its divisors is an integer number (27212588).

Almost surely, 2^81637761 is an apocalyptic number.

It is an amenable number.

81637761 is a deficient number, since it is larger than the sum of its proper divisors (27212591).

81637761 is a wasteful number, since it uses less digits than its factorization.

81637761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27212590.

The product of its digits is 42336, while the sum is 39.

The square root of 81637761 is about 9035.3616972427. The cubic root of 81637761 is about 433.8074722794.

The spelling of 81637761 in words is "eighty-one million, six hundred thirty-seven thousand, seven hundred sixty-one".