21901749 has 24 divisors (see below), whose sum is σ = 30931296. Its totient is φ = 13776000.

The previous prime is 21901739. The next prime is 21901751. The reversal of 21901749 is 94710912.

It is a de Polignac number, because none of the positive numbers 2^k-21901749 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21901709) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 216799 + ... + 216899.

It is an arithmetic number, because the mean of its divisors is an integer number (1288804).

Almost surely, 2^21901749 is an apocalyptic number.

It is an amenable number.

21901749 is a deficient number, since it is larger than the sum of its proper divisors (9029547).

21901749 is a wasteful number, since it uses less digits than its factorization.

21901749 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 229 (or 188 counting only the distinct ones).

The product of its (nonzero) digits is 4536, while the sum is 33.

The square root of 21901749 is about 4679.9304482011. The cubic root of 21901749 is about 279.7861845555.

The spelling of 21901749 in words is "twenty-one million, nine hundred one thousand, seven hundred forty-nine".