21000232251 has 6 divisors (see below), whose sum is σ = 30333668820. Its totient is φ = 14000154828.

The previous prime is 21000232247. The next prime is 21000232313. The reversal of 21000232251 is 15223200012.

It is not a de Polignac number, because 21000232251 - 2² = 21000232247 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21000232151) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1166679561 + ... + 1166679578.

It is an arithmetic number, because the mean of its divisors is an integer number (5055611470).

Almost surely, 2^21000232251 is an apocalyptic number.

21000232251 is a deficient number, since it is larger than the sum of its proper divisors (9333436569).

21000232251 is a wasteful number, since it uses less digits than its factorization.

21000232251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2333359145 (or 2333359142 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

Adding to 21000232251 its reverse (15223200012), we get a palindrome (36223432263).

The spelling of 21000232251 in words is "twenty-one billion, two hundred thirty-two thousand, two hundred fifty-one".