21297751 has 2 divisors, whose sum is σ = 21297752. Its totient is φ = 21297750.

The previous prime is 21297733. The next prime is 21297763. The reversal of 21297751 is 15779212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21297751 - 2¹⁷ = 21166679 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21297791) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10648875 + 10648876.

It is an arithmetic number, because the mean of its divisors is an integer number (10648876).

Almost surely, 2^21297751 is an apocalyptic number.

21297751 is a deficient number, since it is larger than the sum of its proper divisors (1).

21297751 is an equidigital number, since it uses as much as digits as its factorization.

21297751 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8820, while the sum is 34.

The square root of 21297751 is about 4614.9486454347. The cubic root of 21297751 is about 277.1902276067.

The spelling of 21297751 in words is "twenty-one million, two hundred ninety-seven thousand, seven hundred fifty-one".