21521851856401 has 16 divisors (see below), whose sum is σ = 23718884555520. Its totient is φ = 19402274384640.

The previous prime is 21521851856389. The next prime is 21521851856437. The reversal of 21521851856401 is 10465815812512.

It is a cyclic number.

It is not a de Polignac number, because 21521851856401 - 2¹¹ = 21521851854353 is a prime.

It is a super-3 number, since 3×21521851856401³ (a number of 41 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21521851826401) 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, 3300360 + ... + 7344118.

It is an arithmetic number, because the mean of its divisors is an integer number (1482430284720).

Almost surely, 2^{21521851856401} is an apocalyptic number.

It is an amenable number.

21521851856401 is a deficient number, since it is larger than the sum of its proper divisors (2197032699119).

21521851856401 is a wasteful number, since it uses less digits than its factorization.

21521851856401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4053336.

The product of its (nonzero) digits is 768000, while the sum is 49.

The spelling of 21521851856401 in words is "twenty-one trillion, five hundred twenty-one billion, eight hundred fifty-one million, eight hundred fifty-six thousand, four hundred one".