21378819650 has 12 divisors (see below), whose sum is σ = 39764604642. Its totient is φ = 8551527840.

The previous prime is 21378819617. The next prime is 21378819653. The reversal of 21378819650 is 5691887312.

It can be written as a sum of positive squares in 3 ways, for example, as 14687743249 + 6691076401 = 121193^2 + 81799^2 .

It is a super-2 number, since 2×21378819650² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (50), and also a Moran number because the ratio is a prime number: 427576393 = 21378819650 / (2 + 1 + 3 + 7 + 8 + 8 + 1 + 9 + 6 + 5 + 0).

It is not an unprimeable number, because it can be changed into a prime (21378819653) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 213788147 + ... + 213788246.

Almost surely, 2^21378819650 is an apocalyptic number.

21378819650 is a deficient number, since it is larger than the sum of its proper divisors (18385784992).

21378819650 is a wasteful number, since it uses less digits than its factorization.

21378819650 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 427576405 (or 427576400 counting only the distinct ones).

The product of its (nonzero) digits is 725760, while the sum is 50.

The spelling of 21378819650 in words is "twenty-one billion, three hundred seventy-eight million, eight hundred nineteen thousand, six hundred fifty".