21721051085377 has 4 divisors (see below), whose sum is σ = 24824058383296. Its totient is φ = 18618043787460.

The previous prime is 21721051085287. The next prime is 21721051085387. The reversal of 21721051085377 is 77358015012712.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21721051085377 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21721051085377.

It is not an unprimeable number, because it can be changed into a prime (21721051085387) 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 in 3 ways as a sum of consecutive naturals, for example, 1551503648949 + ... + 1551503648962.

It is an arithmetic number, because the mean of its divisors is an integer number (6206014595824).

Almost surely, 2^{21721051085377} is an apocalyptic number.

It is an amenable number.

21721051085377 is a deficient number, since it is larger than the sum of its proper divisors (3103007297919).

21721051085377 is an equidigital number, since it uses as much as digits as its factorization.

21721051085377 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3103007297918.

The product of its (nonzero) digits is 823200, while the sum is 49.

The spelling of 21721051085377 in words is "twenty-one trillion, seven hundred twenty-one billion, fifty-one million, eighty-five thousand, three hundred seventy-seven".