21160051721 has 2 divisors, whose sum is σ = 21160051722. Its totient is φ = 21160051720.

The previous prime is 21160051699. The next prime is 21160051733. The reversal of 21160051721 is 12715006112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17997564025 + 3162487696 = 134155^2 + 56236^2 .

It is a cyclic number.

It is not a de Polignac number, because 21160051721 - 2¹⁸ = 21159789577 is a prime.

It is not a weakly prime, because it can be changed into another prime (21160051741) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10580025860 + 10580025861.

It is an arithmetic number, because the mean of its divisors is an integer number (10580025861).

Almost surely, 2^21160051721 is an apocalyptic number.

It is an amenable number.

21160051721 is a deficient number, since it is larger than the sum of its proper divisors (1).

21160051721 is an equidigital number, since it uses as much as digits as its factorization.

21160051721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 840, while the sum is 26.

Adding to 21160051721 its reverse (12715006112), we get a palindrome (33875057833).

The spelling of 21160051721 in words is "twenty-one billion, one hundred sixty million, fifty-one thousand, seven hundred twenty-one".