21057666825501 has 12 divisors (see below), whose sum is σ = 32205843380412. Its totient is φ = 13212653694336.

The previous prime is 21057666825499. The next prime is 21057666825523. The reversal of 21057666825501 is 10552866675012.

It can be written as a sum of positive squares in 2 ways, for example, as 5693234602500 + 15364432223001 = 2386050^2 + 3919749^2 .

It is not a de Polignac number, because 21057666825501 - 2¹ = 21057666825499 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21057666825541) 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 in 11 ways as a sum of consecutive naturals, for example, 68815904506 + ... + 68815904811.

It is an arithmetic number, because the mean of its divisors is an integer number (2683820281701).

Almost surely, 2^{21057666825501} is an apocalyptic number.

It is an amenable number.

21057666825501 is a deficient number, since it is larger than the sum of its proper divisors (11148176554911).

21057666825501 is a wasteful number, since it uses less digits than its factorization.

21057666825501 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 137631809340 (or 137631809337 counting only the distinct ones).

The product of its (nonzero) digits is 6048000, while the sum is 54.

The spelling of 21057666825501 in words is "twenty-one trillion, fifty-seven billion, six hundred sixty-six million, eight hundred twenty-five thousand, five hundred one".