21251002111 has 4 divisors (see below), whose sum is σ = 21252248424. Its totient is φ = 21249755800.

The previous prime is 21251002109. The next prime is 21251002117. The reversal of 21251002111 is 11120015212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21251002111 - 2¹ = 21251002109 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 (21251002117) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 597220 + ... + 631801.

It is an arithmetic number, because the mean of its divisors is an integer number (5313062106).

Almost surely, 2^21251002111 is an apocalyptic number.

21251002111 is a deficient number, since it is larger than the sum of its proper divisors (1246313).

21251002111 is a wasteful number, since it uses less digits than its factorization.

21251002111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1246312.

The product of its (nonzero) digits is 40, while the sum is 16.

Adding to 21251002111 its reverse (11120015212), we get a palindrome (32371017323).

The spelling of 21251002111 in words is "twenty-one billion, two hundred fifty-one million, two thousand, one hundred eleven".