81709641 has 60 divisors (see below), whose sum is σ = 136046592. Its totient is φ = 48825504.

The previous prime is 81709619. The next prime is 81709643. The reversal of 81709641 is 14690718.

81709641 is a `hidden beast` number, since 8 + 1 + 7 + 0 + 9 + 641 = 666.

It is not a de Polignac number, because 81709641 - 2⁶ = 81709577 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 81709596 and 81709605.

It is not an unprimeable number, because it can be changed into a prime (81709643) by changing a digit.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 643320 + ... + 643446.

Almost surely, 2^81709641 is an apocalyptic number.

81709641 is a gapful number since it is divisible by the number (81) formed by its first and last digit.

It is an amenable number.

81709641 is a deficient number, since it is larger than the sum of its proper divisors (54336951).

81709641 is a wasteful number, since it uses less digits than its factorization.

81709641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 212 (or 190 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 36.

The square root of 81709641 is about 9039.3385266844. The cubic root of 81709641 is about 433.9347537953.

The spelling of 81709641 in words is "eighty-one million, seven hundred nine thousand, six hundred forty-one".