20720856687437 has 2 divisors, whose sum is σ = 20720856687438. Its totient is φ = 20720856687436.

The previous prime is 20720856687389. The next prime is 20720856687491. The reversal of 20720856687437 is 73478665802702.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17931786344836 + 2789070342601 = 4234594^2 + 1670051^2 .

It is a cyclic number.

It is not a de Polignac number, because 20720856687437 - 2³⁶ = 20652137210701 is a prime.

It is a super-2 number, since 2×20720856687437² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20720856987437) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10360428343718 + 10360428343719.

It is an arithmetic number, because the mean of its divisors is an integer number (10360428343719).

Almost surely, 2^{20720856687437} is an apocalyptic number.

It is an amenable number.

20720856687437 is a deficient number, since it is larger than the sum of its proper divisors (1).

20720856687437 is an equidigital number, since it uses as much as digits as its factorization.

20720856687437 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 189665280, while the sum is 65.

The spelling of 20720856687437 in words is "twenty trillion, seven hundred twenty billion, eight hundred fifty-six million, six hundred eighty-seven thousand, four hundred thirty-seven".