21211556939 has 2 divisors, whose sum is σ = 21211556940. Its totient is φ = 21211556938.

The previous prime is 21211556837. The next prime is 21211556953. The reversal of 21211556939 is 93965511212.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21211556939 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21211556939.

It is not a weakly prime, because it can be changed into another prime (21211556039) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605778469 + 10605778470.

It is an arithmetic number, because the mean of its divisors is an integer number (10605778470).

Almost surely, 2^21211556939 is an apocalyptic number.

21211556939 is a deficient number, since it is larger than the sum of its proper divisors (1).

21211556939 is an equidigital number, since it uses as much as digits as its factorization.

21211556939 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 145800, while the sum is 44.

The spelling of 21211556939 in words is "twenty-one billion, two hundred eleven million, five hundred fifty-six thousand, nine hundred thirty-nine".