21355420360521 has 16 divisors (see below), whose sum is σ = 32278098251840. Its totient is φ = 12450123610560.

The previous prime is 21355420360517. The next prime is 21355420360537. The reversal of 21355420360521 is 12506302455312.

It is not a de Polignac number, because 21355420360521 - 2² = 21355420360517 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21355420360521.

It is not an unprimeable number, because it can be changed into a prime (21355420360541) 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, 14409864550 + ... + 14409866031.

It is an arithmetic number, because the mean of its divisors is an integer number (2017381140740).

Almost surely, 2^{21355420360521} is an apocalyptic number.

It is an amenable number.

21355420360521 is a deficient number, since it is larger than the sum of its proper divisors (10922677891319).

21355420360521 is a wasteful number, since it uses less digits than its factorization.

21355420360521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28819730616.

The product of its (nonzero) digits is 216000, while the sum is 39.

The spelling of 21355420360521 in words is "twenty-one trillion, three hundred fifty-five billion, four hundred twenty million, three hundred sixty thousand, five hundred twenty-one".