21009783673 has 2 divisors, whose sum is σ = 21009783674. Its totient is φ = 21009783672.

The previous prime is 21009783611. The next prime is 21009783701. The reversal of 21009783673 is 37638790012.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15288827904 + 5720955769 = 123648^2 + 75637^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21009783673 is a prime.

It is a super-2 number, since 2×21009783673² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21009783073) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10504891836 + 10504891837.

It is an arithmetic number, because the mean of its divisors is an integer number (10504891837).

Almost surely, 2^21009783673 is an apocalyptic number.

It is an amenable number.

21009783673 is a deficient number, since it is larger than the sum of its proper divisors (1).

21009783673 is an equidigital number, since it uses as much as digits as its factorization.

21009783673 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 381024, while the sum is 46.

The spelling of 21009783673 in words is "twenty-one billion, nine million, seven hundred eighty-three thousand, six hundred seventy-three".