21851417537 has 2 divisors, whose sum is σ = 21851417538. Its totient is φ = 21851417536.

The previous prime is 21851417509. The next prime is 21851417573. The reversal of 21851417537 is 73571415812.

Together with next prime (21851417573) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21820902961 + 30514576 = 147719^2 + 5524^2 .

It is a cyclic number.

It is not a de Polignac number, because 21851417537 - 2⁸ = 21851417281 is a prime.

It is a super-2 number, since 2×21851417537² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21851413537) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10925708768 + 10925708769.

It is an arithmetic number, because the mean of its divisors is an integer number (10925708769).

Almost surely, 2^21851417537 is an apocalyptic number.

It is an amenable number.

21851417537 is a deficient number, since it is larger than the sum of its proper divisors (1).

21851417537 is an equidigital number, since it uses as much as digits as its factorization.

21851417537 is an evil number, because the sum of its binary digits is even.

The product of its digits is 235200, while the sum is 44.

The spelling of 21851417537 in words is "twenty-one billion, eight hundred fifty-one million, four hundred seventeen thousand, five hundred thirty-seven".