1005721998 has 16 divisors (see below), whose sum is σ = 2016700416. Its totient is φ = 334364600.

The previous prime is 1005721991. The next prime is 1005721999. The reversal of 1005721998 is 8991275001.

It is a super-2 number, since 2×1005721998² = 2022953474522224008, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1005721991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 216528 + ... + 221123.

It is an arithmetic number, because the mean of its divisors is an integer number (126043776).

Almost surely, 2^1005721998 is an apocalyptic number.

1005721998 is an abundant number, since it is smaller than the sum of its proper divisors (1010978418).

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

1005721998 is a wasteful number, since it uses less digits than its factorization.

1005721998 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 438039.

The product of its (nonzero) digits is 45360, while the sum is 42.

The square root of 1005721998 is about 31713.1202816752. The cubic root of 1005721998 is about 1001.9037062694.

Adding to 1005721998 its reverse (8991275001), we get a palindrome (9996996999).

It can be divided in two parts, 1005 and 721998, that added together give a triangular number (723003 = T₁₂₀₂).

The spelling of 1005721998 in words is "one billion, five million, seven hundred twenty-one thousand, nine hundred ninety-eight".