21787149 has 16 divisors (see below), whose sum is σ = 31821120. Its totient is φ = 13198080.

The previous prime is 21787147. The next prime is 21787163. The reversal of 21787149 is 94178712.

It is not a de Polignac number, because 21787149 - 2¹ = 21787147 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21787147) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5887 + ... + 8844.

It is an arithmetic number, because the mean of its divisors is an integer number (1988820).

Almost surely, 2^21787149 is an apocalyptic number.

21787149 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

21787149 is a deficient number, since it is larger than the sum of its proper divisors (10033971).

21787149 is a wasteful number, since it uses less digits than its factorization.

21787149 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14780.

The product of its digits is 28224, while the sum is 39.

The square root of 21787149 is about 4667.6706181992. The cubic root of 21787149 is about 279.2973410462.

The spelling of 21787149 in words is "twenty-one million, seven hundred eighty-seven thousand, one hundred forty-nine".