21194412780121 has 27 divisors (see below), whose sum is σ = 25130710809981. Its totient is φ = 17822436375744.

The previous prime is 21194412780119. The next prime is 21194412780161. The reversal of 21194412780121 is 12108721449112.

The square root of 21194412780121 is 4603739.

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

It can be written as a sum of positive squares in 4 ways, for example, as 3083975015625 + 18110437764496 = 1756125^2 + 4255636^2 .

It is not a de Polignac number, because 21194412780121 - 2¹ = 21194412780119 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21194412780161) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 1707980965 + ... + 1707993373.

Almost surely, 2^{21194412780121} is an apocalyptic number.

21194412780121 is the 4603739-th square number.

21194412780121 is the 2301870-th centered octagonal number.

It is an amenable number.

21194412780121 is a deficient number, since it is larger than the sum of its proper divisors (3936298029860).

21194412780121 is an frugal number, since it uses more digits than its factorization.

21194412780121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24938 (or 12469 counting only the distinct ones).

The product of its (nonzero) digits is 64512, while the sum is 43.

The spelling of 21194412780121 in words is "twenty-one trillion, one hundred ninety-four billion, four hundred twelve million, seven hundred eighty thousand, one hundred twenty-one".