21549399 has 8 divisors (see below), whose sum is σ = 28899312. Its totient is φ = 14282880.

The previous prime is 21549397. The next prime is 21549427. The reversal of 21549399 is 99394512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21549399 - 2¹ = 21549397 is a prime.

It is a super-2 number, since 2×21549399² = 928753194522402, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21549399.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21549391) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20242 + ... + 21279.

It is an arithmetic number, because the mean of its divisors is an integer number (3612414).

Almost surely, 2^21549399 is an apocalyptic number.

21549399 is a deficient number, since it is larger than the sum of its proper divisors (7349913).

21549399 is a wasteful number, since it uses less digits than its factorization.

21549399 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41697.

The product of its digits is 87480, while the sum is 42.

The square root of 21549399 is about 4642.1330226524. The cubic root of 21549399 is about 278.2776886463.

The spelling of 21549399 in words is "twenty-one million, five hundred forty-nine thousand, three hundred ninety-nine".