21001555455 has 16 divisors (see below), whose sum is σ = 35579106144. Its totient is φ = 10541957120.

The previous prime is 21001555441. The next prime is 21001555469. The reversal of 21001555455 is 55455510012.

It is an interprime number because it is at equal distance from previous prime (21001555441) and next prime (21001555469).

It is not a de Polignac number, because 21001555455 - 2⁶ = 21001555391 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 41179266 + ... + 41179775.

It is an arithmetic number, because the mean of its divisors is an integer number (2223694134).

Almost surely, 2^21001555455 is an apocalyptic number.

21001555455 is a deficient number, since it is larger than the sum of its proper divisors (14577550689).

21001555455 is a wasteful number, since it uses less digits than its factorization.

21001555455 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82359066.

The product of its (nonzero) digits is 25000, while the sum is 33.

The spelling of 21001555455 in words is "twenty-one billion, one million, five hundred fifty-five thousand, four hundred fifty-five".