19721989225 has 9 divisors (see below), whose sum is σ = 24456137367. Its totient is φ = 15777029640.

The previous prime is 19721989213. The next prime is 19721989247. The reversal of 19721989225 is 52298912791.

The square root of 19721989225 is 140435.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 7099916121 + 12622073104 = 84261^2 + 112348^2 .

It is not a de Polignac number, because 19721989225 - 2⁷ = 19721989097 is a prime.

It is a super-2 number, since 2×19721989225² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

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 8 ways as a sum of consecutive naturals, for example, 688132 + ... + 716218.

Almost surely, 2^19721989225 is an apocalyptic number.

19721989225 is the 140435-th square number.

19721989225 is the 70218-th centered octagonal number.

It is an amenable number.

19721989225 is a deficient number, since it is larger than the sum of its proper divisors (4734148142).

19721989225 is an frugal number, since it uses more digits than its factorization.

19721989225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56184 (or 28092 counting only the distinct ones).

The product of its digits is 1632960, while the sum is 55.

The spelling of 19721989225 in words is "nineteen billion, seven hundred twenty-one million, nine hundred eighty-nine thousand, two hundred twenty-five".