20851557437 has 2 divisors, whose sum is σ = 20851557438. Its totient is φ = 20851557436.

The previous prime is 20851557401. The next prime is 20851557439. The reversal of 20851557437 is 73475515802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20435846116 + 415711321 = 142954^2 + 20389^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20851557437 is a prime.

It is a super-3 number, since 3×20851557437³ (a number of 32 digits) contains 333 as substring.

Together with 20851557439, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 20851557391 and 20851557400.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20851557439) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10425778718 + 10425778719.

It is an arithmetic number, because the mean of its divisors is an integer number (10425778719).

Almost surely, 2^20851557437 is an apocalyptic number.

It is an amenable number.

20851557437 is a deficient number, since it is larger than the sum of its proper divisors (1).

20851557437 is an equidigital number, since it uses as much as digits as its factorization.

20851557437 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1176000, while the sum is 47.

The spelling of 20851557437 in words is "twenty billion, eight hundred fifty-one million, five hundred fifty-seven thousand, four hundred thirty-seven".