21015521455 has 8 divisors (see below), whose sum is σ = 25219780704. Its totient is φ = 16811647200.

The previous prime is 21015521453. The next prime is 21015521503. The reversal of 21015521455 is 55412551012.

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

It is not a de Polignac number, because 21015521455 - 2¹ = 21015521453 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21015521453) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 41865 + ... + 209245.

It is an arithmetic number, because the mean of its divisors is an integer number (3152472588).

Almost surely, 2^21015521455 is an apocalyptic number.

21015521455 is a deficient number, since it is larger than the sum of its proper divisors (4204259249).

21015521455 is a wasteful number, since it uses less digits than its factorization.

21015521455 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 192497.

The product of its (nonzero) digits is 10000, while the sum is 31.

The spelling of 21015521455 in words is "twenty-one billion, fifteen million, five hundred twenty-one thousand, four hundred fifty-five".