81215801650 has 24 divisors (see below), whose sum is σ = 151113804660. Its totient is φ = 32475048960.

The previous prime is 81215801647. The next prime is 81215801657. The reversal of 81215801650 is 5610851218.

It can be written as a sum of positive squares in 6 ways, for example, as 5032625481 + 76183176169 = 70941^2 + 276013^2 .

It is not an unprimeable number, because it can be changed into a prime (81215801657) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 135495 + ... + 425194.

Almost surely, 2^81215801650 is an apocalyptic number.

81215801650 is a deficient number, since it is larger than the sum of its proper divisors (69898003010).

81215801650 is a wasteful number, since it uses less digits than its factorization.

81215801650 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 563598 (or 563593 counting only the distinct ones).

The product of its (nonzero) digits is 19200, while the sum is 37.

The spelling of 81215801650 in words is "eighty-one billion, two hundred fifteen million, eight hundred one thousand, six hundred fifty".