81221541 has 16 divisors (see below), whose sum is σ = 109695360. Its totient is φ = 53452800.

The previous prime is 81221537. The next prime is 81221573. The reversal of 81221541 is 14512218.

It is not a de Polignac number, because 81221541 - 2² = 81221537 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81221641) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 86965 + ... + 87893.

It is an arithmetic number, because the mean of its divisors is an integer number (6855960).

Almost surely, 2^81221541 is an apocalyptic number.

It is an amenable number.

81221541 is a deficient number, since it is larger than the sum of its proper divisors (28473819).

81221541 is a wasteful number, since it uses less digits than its factorization.

81221541 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1276.

The product of its digits is 640, while the sum is 24.

The square root of 81221541 is about 9012.2994291135. The cubic root of 81221541 is about 433.0689779473.

Adding to 81221541 its reverse (14512218), we get a palindrome (95733759).

The spelling of 81221541 in words is "eighty-one million, two hundred twenty-one thousand, five hundred forty-one".