21851683537 has 2 divisors, whose sum is σ = 21851683538. Its totient is φ = 21851683536.

The previous prime is 21851683507. The next prime is 21851683547. The reversal of 21851683537 is 73538615812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19375526416 + 2476157121 = 139196^2 + 49761^2 .

It is a cyclic number.

It is not a de Polignac number, because 21851683537 - 2⁷ = 21851683409 is a prime.

It is not a weakly prime, because it can be changed into another prime (21851683507) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10925841768 + 10925841769.

It is an arithmetic number, because the mean of its divisors is an integer number (10925841769).

Almost surely, 2^21851683537 is an apocalyptic number.

It is an amenable number.

21851683537 is a deficient number, since it is larger than the sum of its proper divisors (1).

21851683537 is an equidigital number, since it uses as much as digits as its factorization.

21851683537 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1209600, while the sum is 49.

The spelling of 21851683537 in words is "twenty-one billion, eight hundred fifty-one million, six hundred eighty-three thousand, five hundred thirty-seven".