21621628673 has 2 divisors, whose sum is σ = 21621628674. Its totient is φ = 21621628672.

The previous prime is 21621628667. The next prime is 21621628729. The reversal of 21621628673 is 37682612612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14201012224 + 7420616449 = 119168^2 + 86143^2 .

It is a cyclic number.

It is not a de Polignac number, because 21621628673 - 2⁴ = 21621628657 is a prime.

It is not a weakly prime, because it can be changed into another prime (21621628603) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10810814336 + 10810814337.

It is an arithmetic number, because the mean of its divisors is an integer number (10810814337).

Almost surely, 2^21621628673 is an apocalyptic number.

It is an amenable number.

21621628673 is a deficient number, since it is larger than the sum of its proper divisors (1).

21621628673 is an equidigital number, since it uses as much as digits as its factorization.

21621628673 is an evil number, because the sum of its binary digits is even.

The product of its digits is 290304, while the sum is 44.

The spelling of 21621628673 in words is "twenty-one billion, six hundred twenty-one million, six hundred twenty-eight thousand, six hundred seventy-three".