21123781337 has 12 divisors (see below), whose sum is σ = 22185498816. Its totient is φ = 20108059440.

The previous prime is 21123781303. The next prime is 21123781351. The reversal of 21123781337 is 73318732112.

It is a de Polignac number, because none of the positive numbers 2^k-21123781337 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21123781337.

It is not an unprimeable number, because it can be changed into a prime (21123781397) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 117173 + ... + 236594.

It is an arithmetic number, because the mean of its divisors is an integer number (1848791568).

Almost surely, 2^21123781337 is an apocalyptic number.

It is an amenable number.

21123781337 is a deficient number, since it is larger than the sum of its proper divisors (1061717479).

21123781337 is an equidigital number, since it uses as much as digits as its factorization.

21123781337 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 353896 (or 353867 counting only the distinct ones).

The product of its digits is 42336, while the sum is 38.

The spelling of 21123781337 in words is "twenty-one billion, one hundred twenty-three million, seven hundred eighty-one thousand, three hundred thirty-seven".