81409661 has 8 divisors (see below), whose sum is σ = 86210880. Its totient is φ = 76660128.

The previous prime is 81409649. The next prime is 81409663. The reversal of 81409661 is 16690418.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81409661 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81409663) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9656 + ... + 16001.

It is an arithmetic number, because the mean of its divisors is an integer number (10776360).

Almost surely, 2^81409661 is an apocalyptic number.

It is an amenable number.

81409661 is a deficient number, since it is larger than the sum of its proper divisors (4801219).

81409661 is a wasteful number, since it uses less digits than its factorization.

81409661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25843.

The product of its (nonzero) digits is 10368, while the sum is 35.

The square root of 81409661 is about 9022.7302408972. The cubic root of 81409661 is about 433.4030687902.

The spelling of 81409661 in words is "eighty-one million, four hundred nine thousand, six hundred sixty-one".