21981324121 has 9 divisors (see below), whose sum is σ = 22134946621. Its totient is φ = 21828763552.

The previous prime is 21981324119. The next prime is 21981324149. The reversal of 21981324121 is 12142318912.

The square root of 21981324121 is 148261.

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 15391131721 + 6590192400 = 124061^2 + 81180^2 .

It is not a de Polignac number, because 21981324121 - 2¹ = 21981324119 is a prime.

It is a super-2 number, since 2×21981324121² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21981324821) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 25648725 + ... + 25649581.

Almost surely, 2^21981324121 is an apocalyptic number.

21981324121 is the 148261-st square number.

21981324121 is the 74131-st centered octagonal number.

It is an amenable number.

21981324121 is a deficient number, since it is larger than the sum of its proper divisors (153622500).

21981324121 is an frugal number, since it uses more digits than its factorization.

21981324121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2060 (or 1030 counting only the distinct ones).

The product of its digits is 6912, while the sum is 34.

The spelling of 21981324121 in words is "twenty-one billion, nine hundred eighty-one million, three hundred twenty-four thousand, one hundred twenty-one".