81210531 has 16 divisors (see below), whose sum is σ = 111693824. Its totient is φ = 52454304.

The previous prime is 81210511. The next prime is 81210587. The reversal of 81210531 is 13501218.

It is not a de Polignac number, because 81210531 - 2¹¹ = 81208483 is a prime.

It is a super-2 number, since 2×81210531² = 13190300690603922, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81210498 and 81210507.

It is not an unprimeable number, because it can be changed into a prime (81210511) 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, 13905 + ... + 18861.

It is an arithmetic number, because the mean of its divisors is an integer number (6980864).

Almost surely, 2^81210531 is an apocalyptic number.

81210531 is a deficient number, since it is larger than the sum of its proper divisors (30483293).

81210531 is a wasteful number, since it uses less digits than its factorization.

81210531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5130.

The product of its (nonzero) digits is 240, while the sum is 21.

The square root of 81210531 is about 9011.6885765100. The cubic root of 81210531 is about 433.0494088164.

Adding to 81210531 its reverse (13501218), we get a palindrome (94711749).

The spelling of 81210531 in words is "eighty-one million, two hundred ten thousand, five hundred thirty-one".