1621499921 has 2 divisors, whose sum is σ = 1621499922. Its totient is φ = 1621499920.

The previous prime is 1621499911. The next prime is 1621499923. The reversal of 1621499921 is 1299941261.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1157700625 + 463799296 = 34025^2 + 21536^2 .

It is a cyclic number.

It is not a de Polignac number, because 1621499921 - 2³⁰ = 547758097 is a prime.

Together with 1621499923, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (1621499923) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 810749960 + 810749961.

It is an arithmetic number, because the mean of its divisors is an integer number (810749961).

Almost surely, 2^1621499921 is an apocalyptic number.

It is an amenable number.

1621499921 is a deficient number, since it is larger than the sum of its proper divisors (1).

1621499921 is an equidigital number, since it uses as much as digits as its factorization.

1621499921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 69984, while the sum is 44.

The square root of 1621499921 is about 40267.8522024704. The cubic root of 1621499921 is about 1174.8226491945.

The spelling of 1621499921 in words is "one billion, six hundred twenty-one million, four hundred ninety-nine thousand, nine hundred twenty-one".