21609728783971 has 2 divisors, whose sum is σ = 21609728783972. Its totient is φ = 21609728783970.

The previous prime is 21609728783941. The next prime is 21609728784031. The reversal of 21609728783971 is 17938782790612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21609728783971 - 2⁵ = 21609728783939 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21609728783971.

It is not a weakly prime, because it can be changed into another prime (21609728783921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10804864391985 + 10804864391986.

It is an arithmetic number, because the mean of its divisors is an integer number (10804864391986).

Almost surely, 2^{21609728783971} is an apocalyptic number.

21609728783971 is a deficient number, since it is larger than the sum of its proper divisors (1).

21609728783971 is an equidigital number, since it uses as much as digits as its factorization.

21609728783971 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 128024064, while the sum is 70.

The spelling of 21609728783971 in words is "twenty-one trillion, six hundred nine billion, seven hundred twenty-eight million, seven hundred eighty-three thousand, nine hundred seventy-one".