21641651032621 has 4 divisors (see below), whose sum is σ = 21641661334972. Its totient is φ = 21641640730272.

The previous prime is 21641651032613. The next prime is 21641651032667. The reversal of 21641651032621 is 12623015614612.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 11394769876996 + 10246881155625 = 3375614^2 + 3201075^2 .

It is a cyclic number.

It is not a de Polignac number, because 21641651032621 - 2³ = 21641651032613 is a prime.

It is a super-2 number, since 2×21641651032621² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21641651032721) 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, 742416 + ... + 6620761.

It is an arithmetic number, because the mean of its divisors is an integer number (5410415333743).

Almost surely, 2^{21641651032621} is an apocalyptic number.

It is an amenable number.

21641651032621 is a deficient number, since it is larger than the sum of its proper divisors (10302351).

21641651032621 is an equidigital number, since it uses as much as digits as its factorization.

21641651032621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10302350.

The product of its (nonzero) digits is 103680, while the sum is 40.

The spelling of 21641651032621 in words is "twenty-one trillion, six hundred forty-one billion, six hundred fifty-one million, thirty-two thousand, six hundred twenty-one".