21749951 has 2 divisors, whose sum is σ = 21749952. Its totient is φ = 21749950.

The previous prime is 21749933. The next prime is 21749989. The reversal of 21749951 is 15994712.

It is an a-pointer prime, because the next prime (21749989) can be obtained adding 21749951 to its sum of digits (38).

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21749951 is a prime.

It is a super-4 number, since 4×21749951⁴ (a number of 30 digits) contains 4444 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21749911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10874975 + 10874976.

It is an arithmetic number, because the mean of its divisors is an integer number (10874976).

Almost surely, 2^21749951 is an apocalyptic number.

21749951 is a deficient number, since it is larger than the sum of its proper divisors (1).

21749951 is an equidigital number, since it uses as much as digits as its factorization.

21749951 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 22680, while the sum is 38.

The square root of 21749951 is about 4663.6842731900. The cubic root of 21749951 is about 279.1382989615.

The spelling of 21749951 in words is "twenty-one million, seven hundred forty-nine thousand, nine hundred fifty-one".