181899021636 has 36 divisors (see below), whose sum is σ = 468475787052. Its totient is φ = 59488987584.

The previous prime is 181899021617. The next prime is 181899021637. The reversal of 181899021636 is 636120998181.

It can be written as a sum of positive squares in 2 ways, for example, as 46335145536 + 135563876100 = 215256^2 + 368190^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a super-2 number, since 2×181899021636² (a number of 23 digits) contains 22 as substring.

It is a hoax number, since the sum of its digits (54) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (181899021637) 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, 47665551 + ... + 47669366.

It is an arithmetic number, because the mean of its divisors is an integer number (13013216307).

Almost surely, 2^181899021636 is an apocalyptic number.

It is an amenable number.

181899021636 is an abundant number, since it is smaller than the sum of its proper divisors (286576765416).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

181899021636 is a wasteful number, since it uses less digits than its factorization.

181899021636 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 95334980 (or 95334975 counting only the distinct ones).

The product of its (nonzero) digits is 1119744, while the sum is 54.

The spelling of 181899021636 in words is "one hundred eighty-one billion, eight hundred ninety-nine million, twenty-one thousand, six hundred thirty-six".