21155001505 has 32 divisors (see below), whose sum is σ = 28506193920. Its totient is φ = 14939305920.

The previous prime is 21155001499. The next prime is 21155001509. The reversal of 21155001505 is 50510055112.

It is not a de Polignac number, because 21155001505 - 2⁷ = 21155001377 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21155001505.

It is not an unprimeable number, because it can be changed into a prime (21155001509) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 296076 + ... + 360514.

It is an arithmetic number, because the mean of its divisors is an integer number (890818560).

Almost surely, 2^21155001505 is an apocalyptic number.

It is an amenable number.

21155001505 is a deficient number, since it is larger than the sum of its proper divisors (7351192415).

21155001505 is a wasteful number, since it uses less digits than its factorization.

21155001505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64629.

The product of its (nonzero) digits is 1250, while the sum is 25.

Adding to 21155001505 its reverse (50510055112), we get a palindrome (71665056617).

The spelling of 21155001505 in words is "twenty-one billion, one hundred fifty-five million, one thousand, five hundred five".