20651642521 has 2 divisors, whose sum is σ = 20651642522. Its totient is φ = 20651642520.

The previous prime is 20651642519. The next prime is 20651642567. The reversal of 20651642521 is 12524615602.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14498808921 + 6152833600 = 120411^2 + 78440^2 .

It is a cyclic number.

It is not a de Polignac number, because 20651642521 - 2¹ = 20651642519 is a prime.

Together with 20651642519, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (20651642821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10325821260 + 10325821261.

It is an arithmetic number, because the mean of its divisors is an integer number (10325821261).

Almost surely, 2^20651642521 is an apocalyptic number.

It is an amenable number.

20651642521 is a deficient number, since it is larger than the sum of its proper divisors (1).

20651642521 is an equidigital number, since it uses as much as digits as its factorization.

20651642521 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 28800, while the sum is 34.

The spelling of 20651642521 in words is "twenty billion, six hundred fifty-one million, six hundred forty-two thousand, five hundred twenty-one".