9999977621 has 2 divisors, whose sum is σ = 9999977622. Its totient is φ = 9999977620.

The previous prime is 9999977597. The next prime is 9999977623. The reversal of 9999977621 is 1267799999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9390579025 + 609398596 = 96905^2 + 24686^2 .

It is an emirp because it is prime and its reverse (1267799999) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-9999977621 is a prime.

Together with 9999977623, it forms a pair of twin primes.

It is a Chen prime.

It is a nialpdrome in base 10.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9999977623) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4999988810 + 4999988811.

It is an arithmetic number, because the mean of its divisors is an integer number (4999988811).

Almost surely, 2^9999977621 is an apocalyptic number.

It is an amenable number.

9999977621 is a deficient number, since it is larger than the sum of its proper divisors (1).

9999977621 is an equidigital number, since it uses as much as digits as its factorization.

9999977621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 34720812, while the sum is 68.

The square root of 9999977621 is about 99999.8881049374. Note that the first 3 decimals coincide. The cubic root of 9999977621 is about 2154.4330828942.

The spelling of 9999977621 in words is "nine billion, nine hundred ninety-nine million, nine hundred seventy-seven thousand, six hundred twenty-one".