642121123326521 has 16 divisors (see below), whose sum is σ = 686713144189968. Its totient is φ = 598288445184000.

The previous prime is 642121123326511. The next prime is 642121123326587. The reversal of 642121123326521 is 125623321121246.

It can be written as a sum of positive squares in 8 ways, for example, as 172263000010000 + 469858123316521 = 13124900^2 + 21676211^2 .

It is a de Polignac number, because none of the positive numbers 2^k-642121123326521 is a prime.

It is a super-2 number, since 2×642121123326521² (a number of 30 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (642121123326511) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10806410 + ... + 37430211.

It is an arithmetic number, because the mean of its divisors is an integer number (42919571511873).

Almost surely, 2^{642121123326521} is an apocalyptic number.

It is an amenable number.

642121123326521 is a deficient number, since it is larger than the sum of its proper divisors (44592020863447).

642121123326521 is a wasteful number, since it uses less digits than its factorization.

642121123326521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 48244492.

The product of its digits is 207360, while the sum is 41.

Adding to 642121123326521 its reverse (125623321121246), we get a palindrome (767744444447767).

The spelling of 642121123326521 in words is "six hundred forty-two trillion, one hundred twenty-one billion, one hundred twenty-three million, three hundred twenty-six thousand, five hundred twenty-one".