21101749 has 2 divisors, whose sum is σ = 21101750. Its totient is φ = 21101748.

The previous prime is 21101747. The next prime is 21101753. The reversal of 21101749 is 94710112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21022225 + 79524 = 4585^2 + 282^2 .

It is a cyclic number.

It is not a de Polignac number, because 21101749 - 2¹ = 21101747 is a prime.

Together with 21101747, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21101747) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10550874 + 10550875.

It is an arithmetic number, because the mean of its divisors is an integer number (10550875).

Almost surely, 2^21101749 is an apocalyptic number.

It is an amenable number.

21101749 is a deficient number, since it is larger than the sum of its proper divisors (1).

21101749 is an equidigital number, since it uses as much as digits as its factorization.

21101749 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 504, while the sum is 25.

The square root of 21101749 is about 4593.6640059978. The cubic root of 21101749 is about 276.3372836944.

The spelling of 21101749 in words is "twenty-one million, one hundred one thousand, seven hundred forty-nine".