10521256661 has 2 divisors, whose sum is σ = 10521256662. Its totient is φ = 10521256660.

The previous prime is 10521256657. The next prime is 10521256721. The reversal of 10521256661 is 16665212501.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 5432574436 + 5088682225 = 73706^2 + 71335^2 .

It is a cyclic number.

It is not a de Polignac number, because 10521256661 - 2² = 10521256657 is a prime.

It is a super-2 number, since 2×10521256661² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (10521258661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5260628330 + 5260628331.

It is an arithmetic number, because the mean of its divisors is an integer number (5260628331).

Almost surely, 2^10521256661 is an apocalyptic number.

It is an amenable number.

10521256661 is a deficient number, since it is larger than the sum of its proper divisors (1).

10521256661 is an equidigital number, since it uses as much as digits as its factorization.

10521256661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 21600, while the sum is 35.

The spelling of 10521256661 in words is "ten billion, five hundred twenty-one million, two hundred fifty-six thousand, six hundred sixty-one".