21312751 has 2 divisors, whose sum is σ = 21312752. Its totient is φ = 21312750.

The previous prime is 21312727. The next prime is 21312763. The reversal of 21312751 is 15721312.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21312751 - 2¹⁷ = 21181679 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21312721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10656375 + 10656376.

It is an arithmetic number, because the mean of its divisors is an integer number (10656376).

Almost surely, 2^21312751 is an apocalyptic number.

21312751 is a deficient number, since it is larger than the sum of its proper divisors (1).

21312751 is an equidigital number, since it uses as much as digits as its factorization.

21312751 is an evil number, because the sum of its binary digits is even.

The product of its digits is 420, while the sum is 22.

The square root of 21312751 is about 4616.5735128989. The cubic root of 21312751 is about 277.2552873348.

The spelling of 21312751 in words is "twenty-one million, three hundred twelve thousand, seven hundred fifty-one".