21521851856402 has 8 divisors (see below), whose sum is σ = 32283009619212. Its totient is φ = 10760848650000.

The previous prime is 21521851856389. The next prime is 21521851856437. The reversal of 21521851856402 is 20465815812512.

It can be written as a sum of positive squares in 2 ways, for example, as 20332532923921 + 1189318932481 = 4509161^2 + 1090559^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 38290349 + ... + 38848352.

Almost surely, 2^{21521851856402} is an apocalyptic number.

21521851856402 is a deficient number, since it is larger than the sum of its proper divisors (10761157762810).

21521851856402 is a wasteful number, since it uses less digits than its factorization.

21521851856402 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77278204.

The product of its (nonzero) digits is 1536000, while the sum is 50.

The spelling of 21521851856402 in words is "twenty-one trillion, five hundred twenty-one billion, eight hundred fifty-one million, eight hundred fifty-six thousand, four hundred two".