21305522251 has 12 divisors (see below), whose sum is σ = 23190048408. Its totient is φ = 19564706304.

The previous prime is 21305522239. The next prime is 21305522261. The reversal of 21305522251 is 15222550312.

It is not a de Polignac number, because 21305522251 - 2¹⁵ = 21305489483 is a prime.

It is a super-2 number, since 2×21305522251² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21305522261) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 293985 + ... + 359218.

It is an arithmetic number, because the mean of its divisors is an integer number (1932504034).

Almost surely, 2^21305522251 is an apocalyptic number.

21305522251 is a deficient number, since it is larger than the sum of its proper divisors (1884526157).

21305522251 is a wasteful number, since it uses less digits than its factorization.

21305522251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 653422 (or 653409 counting only the distinct ones).

The product of its (nonzero) digits is 6000, while the sum is 28.

The spelling of 21305522251 in words is "twenty-one billion, three hundred five million, five hundred twenty-two thousand, two hundred fifty-one".