10621666721 has 4 divisors (see below), whose sum is σ = 10621989444. Its totient is φ = 10621344000.

The previous prime is 10621666711. The next prime is 10621666733. The reversal of 10621666721 is 12766612601.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1464133696 + 9157533025 = 38264^2 + 95695^2 .

It is a cyclic number.

It is not a de Polignac number, because 10621666721 - 2²⁶ = 10554557857 is a prime.

It is a super-2 number, since 2×10621666721² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (10621666711) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 105560 + ... + 179961.

It is an arithmetic number, because the mean of its divisors is an integer number (2655497361).

Almost surely, 2^10621666721 is an apocalyptic number.

It is an amenable number.

10621666721 is a deficient number, since it is larger than the sum of its proper divisors (322723).

10621666721 is an equidigital number, since it uses as much as digits as its factorization.

10621666721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 322722.

The product of its (nonzero) digits is 36288, while the sum is 38.

The spelling of 10621666721 in words is "ten billion, six hundred twenty-one million, six hundred sixty-six thousand, seven hundred twenty-one".