21197072251 has 8 divisors (see below), whose sum is σ = 23419783584. Its totient is φ = 19082785920.

The previous prime is 21197072231. The next prime is 21197072257. The reversal of 21197072251 is 15227079112.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21197072251 - 2⁵ = 21197072219 is a prime.

It is a super-2 number, since 2×21197072251² (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 21197072251.

It is not an unprimeable number, because it can be changed into a prime (21197072257) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 27105840 + ... + 27106621.

It is an arithmetic number, because the mean of its divisors is an integer number (2927472948).

Almost surely, 2^21197072251 is an apocalyptic number.

21197072251 is a deficient number, since it is larger than the sum of its proper divisors (2222711333).

21197072251 is a wasteful number, since it uses less digits than its factorization.

21197072251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54212501.

The product of its (nonzero) digits is 17640, while the sum is 37.

The spelling of 21197072251 in words is "twenty-one billion, one hundred ninety-seven million, seventy-two thousand, two hundred fifty-one".