21191153458225 has 9 divisors (see below), whose sum is σ = 26277058829217. Its totient is φ = 16952904353040.

The previous prime is 21191153458207. The next prime is 21191153458243. The reversal of 21191153458225 is 52285435119112.

The square root of 21191153458225 is 4603385.

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

It is an interprime number because it is at equal distance from previous prime (21191153458207) and next prime (21191153458243).

It can be written as a sum of positive squares in 4 ways, for example, as 11320849434609 + 9870304023616 = 3364647^2 + 3141704^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21191153458225 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 22556587 + ... + 23477263.

Almost surely, 2^{21191153458225} is an apocalyptic number.

21191153458225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21191153458225 is the 4603385-th square number.

21191153458225 is the 2301693-rd centered octagonal number.

It is an amenable number.

21191153458225 is a deficient number, since it is larger than the sum of its proper divisors (5085905370992).

21191153458225 is an frugal number, since it uses more digits than its factorization.

21191153458225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1841364 (or 920682 counting only the distinct ones).

The product of its digits is 864000, while the sum is 49.

The spelling of 21191153458225 in words is "twenty-one trillion, one hundred ninety-one billion, one hundred fifty-three million, four hundred fifty-eight thousand, two hundred twenty-five".