81562821 has 8 divisors (see below), whose sum is σ = 115147584. Its totient is φ = 51176640.

The previous prime is 81562799. The next prime is 81562841. The reversal of 81562821 is 12826518.

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

It is not a de Polignac number, because 81562821 - 2⁶ = 81562757 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81562841) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 799585 + ... + 799686.

It is an arithmetic number, because the mean of its divisors is an integer number (14393448).

Almost surely, 2^81562821 is an apocalyptic number.

It is an amenable number.

81562821 is a deficient number, since it is larger than the sum of its proper divisors (33584763).

81562821 is a wasteful number, since it uses less digits than its factorization.

81562821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1599291.

The product of its digits is 7680, while the sum is 33.

The square root of 81562821 is about 9031.2137058094. The cubic root of 81562821 is about 433.6746926927.

It can be divided in two parts, 815 and 62821, that multiplied together give a palindrome (51199115).

The spelling of 81562821 in words is "eighty-one million, five hundred sixty-two thousand, eight hundred twenty-one".