1621221755537 has 2 divisors, whose sum is σ = 1621221755538. Its totient is φ = 1621221755536.

The previous prime is 1621221755477. The next prime is 1621221755567. The reversal of 1621221755537 is 7355571221261.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1213432230481 + 407789525056 = 1101559^2 + 638584^2 .

It is a cyclic number.

It is not a de Polignac number, because 1621221755537 - 2⁸ = 1621221755281 is a prime.

It is a super-3 number, since 3×1621221755537³ (a number of 38 digits) contains 333 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 1621221755491 and 1621221755500.

It is not a weakly prime, because it can be changed into another prime (1621221755567) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 810610877768 + 810610877769.

It is an arithmetic number, because the mean of its divisors is an integer number (810610877769).

Almost surely, 2^{1621221755537} is an apocalyptic number.

It is an amenable number.

1621221755537 is a deficient number, since it is larger than the sum of its proper divisors (1).

1621221755537 is an equidigital number, since it uses as much as digits as its factorization.

1621221755537 is an evil number, because the sum of its binary digits is even.

The product of its digits is 882000, while the sum is 47.

Adding to 1621221755537 its reverse (7355571221261), we get a palindrome (8976792976798).

The spelling of 1621221755537 in words is "one trillion, six hundred twenty-one billion, two hundred twenty-one million, seven hundred fifty-five thousand, five hundred thirty-seven".