21011749 has 4 divisors (see below), whose sum is σ = 22921920. Its totient is φ = 19101580.

The previous prime is 21011741. The next prime is 21011759. The reversal of 21011749 is 94711012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21011749 - 2³ = 21011741 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011741) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 955069 + ... + 955090.

It is an arithmetic number, because the mean of its divisors is an integer number (5730480).

Almost surely, 2^21011749 is an apocalyptic number.

It is an amenable number.

21011749 is a deficient number, since it is larger than the sum of its proper divisors (1910171).

21011749 is a wasteful number, since it uses less digits than its factorization.

21011749 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1910170.

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

The square root of 21011749 is about 4583.8574367011. The cubic root of 21011749 is about 275.9438597920.

The spelling of 21011749 in words is "twenty-one million, eleven thousand, seven hundred forty-nine".