20556721403 has 2 divisors, whose sum is σ = 20556721404. Its totient is φ = 20556721402.

The previous prime is 20556721399. The next prime is 20556721417. The reversal of 20556721403 is 30412765502.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20556721403 - 2² = 20556721399 is a prime.

It is not a weakly prime, because it can be changed into another prime (20556721103) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10278360701 + 10278360702.

It is an arithmetic number, because the mean of its divisors is an integer number (10278360702).

Almost surely, 2^20556721403 is an apocalyptic number.

20556721403 is a deficient number, since it is larger than the sum of its proper divisors (1).

20556721403 is an equidigital number, since it uses as much as digits as its factorization.

20556721403 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 50400, while the sum is 35.

The spelling of 20556721403 in words is "twenty billion, five hundred fifty-six million, seven hundred twenty-one thousand, four hundred three".