21645262381 has 8 divisors (see below), whose sum is σ = 22091916024. Its totient is φ = 21200025600.

The previous prime is 21645262369. The next prime is 21645262391. The reversal of 21645262381 is 18326254612.

It can be written as a sum of positive squares in 4 ways, for example, as 12307905481 + 9337356900 = 110941^2 + 96630^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21645262381 - 2⁷ = 21645262253 is a prime.

It is a super-2 number, since 2×21645262381² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21645262351) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 323320 + ... + 384481.

It is an arithmetic number, because the mean of its divisors is an integer number (2761489503).

Almost surely, 2^21645262381 is an apocalyptic number.

It is an amenable number.

21645262381 is a deficient number, since it is larger than the sum of its proper divisors (446653643).

21645262381 is an equidigital number, since it uses as much as digits as its factorization.

21645262381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 708431.

The product of its digits is 138240, while the sum is 40.

The spelling of 21645262381 in words is "twenty-one billion, six hundred forty-five million, two hundred sixty-two thousand, three hundred eighty-one".