1621975541 has 2 divisors, whose sum is σ = 1621975542. Its totient is φ = 1621975540.

The previous prime is 1621975529. The next prime is 1621975591. The reversal of 1621975541 is 1455791261.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1619740516 + 2235025 = 40246^2 + 1495^2 .

It is a cyclic number.

It is not a de Polignac number, because 1621975541 - 2⁶ = 1621975477 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1621975501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 810987770 + 810987771.

It is an arithmetic number, because the mean of its divisors is an integer number (810987771).

Almost surely, 2^1621975541 is an apocalyptic number.

It is an amenable number.

1621975541 is a deficient number, since it is larger than the sum of its proper divisors (1).

1621975541 is an equidigital number, since it uses as much as digits as its factorization.

1621975541 is an evil number, because the sum of its binary digits is even.

The product of its digits is 75600, while the sum is 41.

The square root of 1621975541 is about 40273.7574730742. The cubic root of 1621975541 is about 1174.9375046888.

The spelling of 1621975541 in words is "one billion, six hundred twenty-one million, nine hundred seventy-five thousand, five hundred forty-one".