21945751 has 2 divisors, whose sum is σ = 21945752. Its totient is φ = 21945750.

The previous prime is 21945689. The next prime is 21945769. The reversal of 21945751 is 15754912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21945751 - 2⁹ = 21945239 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21942751) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10972875 + 10972876.

It is an arithmetic number, because the mean of its divisors is an integer number (10972876).

Almost surely, 2^21945751 is an apocalyptic number.

21945751 is a deficient number, since it is larger than the sum of its proper divisors (1).

21945751 is an equidigital number, since it uses as much as digits as its factorization.

21945751 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12600, while the sum is 34.

The square root of 21945751 is about 4684.6292275910. The cubic root of 21945751 is about 279.9734286010.

The spelling of 21945751 in words is "twenty-one million, nine hundred forty-five thousand, seven hundred fifty-one".