21812631481 has 9 divisors (see below), whose sum is σ = 22024222831. Its totient is φ = 21603057952.

The previous prime is 21812631419. The next prime is 21812631517. The reversal of 21812631481 is 18413621812.

The square root of 21812631481 is 147691.

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., 384356025 + 21428275456 = 19605^2 + 146384^2 .

It is not a de Polignac number, because 21812631481 - 2¹³ = 21812623289 is a prime.

It is a super-2 number, since 2×21812631481² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21812631481.

It is not an unprimeable number, because it can be changed into a prime (21812631781) 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, 16688430 + ... + 16689736.

Almost surely, 2^21812631481 is an apocalyptic number.

21812631481 is the 147691-st square number.

21812631481 is the 73846-th centered octagonal number.

It is an amenable number.

21812631481 is a deficient number, since it is larger than the sum of its proper divisors (211591350).

21812631481 is an frugal number, since it uses more digits than its factorization.

21812631481 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2840 (or 1420 counting only the distinct ones).

The product of its digits is 18432, while the sum is 37.

The spelling of 21812631481 in words is "twenty-one billion, eight hundred twelve million, six hundred thirty-one thousand, four hundred eighty-one".