991653452021 has 4 divisors (see below), whose sum is σ = 991702109100. Its totient is φ = 991604794944.

The previous prime is 991653452003. The next prime is 991653452029. The reversal of 991653452021 is 120254356199.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 697916551396 + 293736900625 = 835414^2 + 541975^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-991653452021 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991653452029) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 24297956 + ... + 24338733.

It is an arithmetic number, because the mean of its divisors is an integer number (247925527275).

Almost surely, 2^991653452021 is an apocalyptic number.

It is an amenable number.

991653452021 is a deficient number, since it is larger than the sum of its proper divisors (48657079).

991653452021 is a wasteful number, since it uses less digits than its factorization.

991653452021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 48657078.

The product of its (nonzero) digits is 583200, while the sum is 47.

The spelling of 991653452021 in words is "nine hundred ninety-one billion, six hundred fifty-three million, four hundred fifty-two thousand, twenty-one".