21199751 has 2 divisors, whose sum is σ = 21199752. Its totient is φ = 21199750.

The previous prime is 21199741. The next prime is 21199781. The reversal of 21199751 is 15799112.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21199751 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21199741) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10599875 + 10599876.

It is an arithmetic number, because the mean of its divisors is an integer number (10599876).

Almost surely, 2^21199751 is an apocalyptic number.

21199751 is a deficient number, since it is larger than the sum of its proper divisors (1).

21199751 is an equidigital number, since it uses as much as digits as its factorization.

21199751 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5670, while the sum is 35.

The square root of 21199751 is about 4604.3187335370. The cubic root of 21199751 is about 276.7644171616.

The spelling of 21199751 in words is "twenty-one million, one hundred ninety-nine thousand, seven hundred fifty-one".