21658749 has 16 divisors (see below), whose sum is σ = 33075840. Its totient is φ = 12349440.

The previous prime is 21658733. The next prime is 21658753. The reversal of 21658749 is 94785612.

It is not a de Polignac number, because 21658749 - 2⁴ = 21658733 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a self number, because there is not a number n which added to its sum of digits gives 21658749.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21658729) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12657 + ... + 14265.

It is an arithmetic number, because the mean of its divisors is an integer number (2067240).

Almost surely, 2^21658749 is an apocalyptic number.

It is an amenable number.

21658749 is a deficient number, since it is larger than the sum of its proper divisors (11417091).

21658749 is a wasteful number, since it uses less digits than its factorization.

21658749 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2260.

The product of its digits is 120960, while the sum is 42.

The square root of 21658749 is about 4653.8961097128. The cubic root of 21658749 is about 278.7475909891.

The spelling of 21658749 in words is "twenty-one million, six hundred fifty-eight thousand, seven hundred forty-nine".