521321011621 has 2 divisors, whose sum is σ = 521321011622. Its totient is φ = 521321011620.

The previous prime is 521321011619. The next prime is 521321011649. The reversal of 521321011621 is 126110123125.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 421110144900 + 100210866721 = 648930^2 + 316561^2 .

It is a cyclic number.

It is not a de Polignac number, because 521321011621 - 2¹ = 521321011619 is a prime.

Together with 521321011619, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (521321011121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 260660505810 + 260660505811.

It is an arithmetic number, because the mean of its divisors is an integer number (260660505811).

Almost surely, 2^521321011621 is an apocalyptic number.

It is an amenable number.

521321011621 is a deficient number, since it is larger than the sum of its proper divisors (1).

521321011621 is an equidigital number, since it uses as much as digits as its factorization.

521321011621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 720, while the sum is 25.

Adding to 521321011621 its reverse (126110123125), we get a palindrome (647431134746).

The spelling of 521321011621 in words is "five hundred twenty-one billion, three hundred twenty-one million, eleven thousand, six hundred twenty-one".