21751091 has 2 divisors, whose sum is σ = 21751092. Its totient is φ = 21751090.

The previous prime is 21751087. The next prime is 21751099. The reversal of 21751091 is 19015712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21751091 - 2² = 21751087 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21751091.

It is not a weakly prime, because it can be changed into another prime (21751099) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10875545 + 10875546.

It is an arithmetic number, because the mean of its divisors is an integer number (10875546).

Almost surely, 2^21751091 is an apocalyptic number.

21751091 is a deficient number, since it is larger than the sum of its proper divisors (1).

21751091 is an equidigital number, since it uses as much as digits as its factorization.

21751091 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 630, while the sum is 26.

The square root of 21751091 is about 4663.8064925552. The cubic root of 21751091 is about 279.1431757863.

The spelling of 21751091 in words is "twenty-one million, seven hundred fifty-one thousand, ninety-one".