81821015 has 8 divisors (see below), whose sum is σ = 98619120. Its totient is φ = 65167552.

The previous prime is 81820967. The next prime is 81821027. The reversal of 81821015 is 51012818.

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

It is a cyclic number.

It is not a de Polignac number, because 81821015 - 2¹⁴ = 81804631 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 34910 + ... + 37179.

It is an arithmetic number, because the mean of its divisors is an integer number (12327390).

Almost surely, 2^81821015 is an apocalyptic number.

81821015 is a deficient number, since it is larger than the sum of its proper divisors (16798105).

81821015 is a wasteful number, since it uses less digits than its factorization.

81821015 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72321.

The product of its (nonzero) digits is 640, while the sum is 26.

The square root of 81821015 is about 9045.4969459947. The cubic root of 81821015 is about 434.1318219627.

The spelling of 81821015 in words is "eighty-one million, eight hundred twenty-one thousand, fifteen".