21502305251 has 16 divisors (see below), whose sum is σ = 25653832704. Its totient is φ = 17621428704.

The previous prime is 21502305239. The next prime is 21502305259. The reversal of 21502305251 is 15250320512.

It is a cyclic number.

It is not a de Polignac number, because 21502305251 - 2¹⁸ = 21502043107 is a prime.

It is a super-2 number, since 2×21502305251² (a number of 21 digits) contains 22 as substring.

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 21502305251.

It is not an unprimeable number, because it can be changed into a prime (21502305259) 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, 351146 + ... + 407808.

It is an arithmetic number, because the mean of its divisors is an integer number (1603364544).

Almost surely, 2^21502305251 is an apocalyptic number.

21502305251 is a deficient number, since it is larger than the sum of its proper divisors (4151527453).

21502305251 is a wasteful number, since it uses less digits than its factorization.

21502305251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 59050.

The product of its (nonzero) digits is 3000, while the sum is 26.

Adding to 21502305251 its reverse (15250320512), we get a palindrome (36752625763).

The spelling of 21502305251 in words is "twenty-one billion, five hundred two million, three hundred five thousand, two hundred fifty-one".