81215357 has 4 divisors (see below), whose sum is σ = 81854976. Its totient is φ = 80575740.

The previous prime is 81215327. The next prime is 81215359. The reversal of 81215357 is 75351218.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81215357 - 2¹⁰ = 81214333 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81215359) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 319619 + ... + 319872.

It is an arithmetic number, because the mean of its divisors is an integer number (20463744).

Almost surely, 2^81215357 is an apocalyptic number.

It is an amenable number.

81215357 is a deficient number, since it is larger than the sum of its proper divisors (639619).

81215357 is a wasteful number, since it uses less digits than its factorization.

81215357 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 639618.

The product of its digits is 8400, while the sum is 32.

The square root of 81215357 is about 9011.9563358907. The cubic root of 81215357 is about 433.0579867476.

The spelling of 81215357 in words is "eighty-one million, two hundred fifteen thousand, three hundred fifty-seven".