81121641 has 8 divisors (see below), whose sum is σ = 110203200. Its totient is φ = 53060592.

The previous prime is 81121633. The next prime is 81121661. The reversal of 81121641 is 14612118.

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

It is not a de Polignac number, because 81121641 - 2³ = 81121633 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81121661) 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, 254941 + ... + 255258.

It is an arithmetic number, because the mean of its divisors is an integer number (13775400).

Almost surely, 2^81121641 is an apocalyptic number.

It is an amenable number.

81121641 is a deficient number, since it is larger than the sum of its proper divisors (29081559).

81121641 is a wasteful number, since it uses less digits than its factorization.

81121641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 510255.

The product of its digits is 384, while the sum is 24.

The square root of 81121641 is about 9006.7552981082. The cubic root of 81121641 is about 432.8913512565.

Adding to 81121641 its reverse (14612118), we get a palindrome (95733759).

The spelling of 81121641 in words is "eighty-one million, one hundred twenty-one thousand, six hundred forty-one".