21553399949 has 6 divisors (see below), whose sum is σ = 22747494510. Its totient is φ = 20419010136.

The previous prime is 21553399943. The next prime is 21553399963. The reversal of 21553399949 is 94999335512.

It can be written as a sum of positive squares in only one way, i.e., 20594259049 + 959140900 = 143507^2 + 30970^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21553399949 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 (21553399943) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 29851994 + ... + 29852715.

It is an arithmetic number, because the mean of its divisors is an integer number (3791249085).

Almost surely, 2^21553399949 is an apocalyptic number.

It is an amenable number.

21553399949 is a deficient number, since it is larger than the sum of its proper divisors (1194094561).

21553399949 is an equidigital number, since it uses as much as digits as its factorization.

21553399949 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 59704747 (or 59704728 counting only the distinct ones).

The product of its digits is 11809800, while the sum is 59.

The spelling of 21553399949 in words is "twenty-one billion, five hundred fifty-three million, three hundred ninety-nine thousand, nine hundred forty-nine".