621561641 has 2 divisors, whose sum is σ = 621561642. Its totient is φ = 621561640.

The previous prime is 621561617. The next prime is 621561643. The reversal of 621561641 is 146165126.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 342805225 + 278756416 = 18515^2 + 16696^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-621561641 is a prime.

It is a super-2 number, since 2×621561641² = 772677747125225762, which contains 22 as substring.

Together with 621561643, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 621561598 and 621561607.

It is not a weakly prime, because it can be changed into another prime (621561643) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 310780820 + 310780821.

It is an arithmetic number, because the mean of its divisors is an integer number (310780821).

Almost surely, 2^621561641 is an apocalyptic number.

It is an amenable number.

621561641 is a deficient number, since it is larger than the sum of its proper divisors (1).

621561641 is an equidigital number, since it uses as much as digits as its factorization.

621561641 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8640, while the sum is 32.

The square root of 621561641 is about 24931.1379804453. The cubic root of 621561641 is about 853.4172197230.

The spelling of 621561641 in words is "six hundred twenty-one million, five hundred sixty-one thousand, six hundred forty-one".