21200551657 has 2 divisors, whose sum is σ = 21200551658. Its totient is φ = 21200551656.

The previous prime is 21200551583. The next prime is 21200551661. The reversal of 21200551657 is 75615500212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20160876121 + 1039675536 = 141989^2 + 32244^2 .

It is a cyclic number.

It is not a de Polignac number, because 21200551657 - 2¹¹ = 21200549609 is a prime.

It is a super-2 number, since 2×21200551657² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21200555657) 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, 10600275828 + 10600275829.

It is an arithmetic number, because the mean of its divisors is an integer number (10600275829).

Almost surely, 2^21200551657 is an apocalyptic number.

It is an amenable number.

21200551657 is a deficient number, since it is larger than the sum of its proper divisors (1).

21200551657 is an equidigital number, since it uses as much as digits as its factorization.

21200551657 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 21000, while the sum is 34.

The spelling of 21200551657 in words is "twenty-one billion, two hundred million, five hundred fifty-one thousand, six hundred fifty-seven".