21553649 has 16 divisors (see below), whose sum is σ = 24299520. Its totient is φ = 18982080.

The previous prime is 21553643. The next prime is 21553717. The reversal of 21553649 is 94635512.

It is not a de Polignac number, because 21553649 - 2⁴ = 21553633 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21553643) 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, 31499 + ... + 32175.

It is an arithmetic number, because the mean of its divisors is an integer number (1518720).

Almost surely, 2^21553649 is an apocalyptic number.

It is an amenable number.

21553649 is a deficient number, since it is larger than the sum of its proper divisors (2745871).

21553649 is a wasteful number, since it uses less digits than its factorization.

21553649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 800.

The product of its digits is 32400, while the sum is 35.

The square root of 21553649 is about 4642.5907637870. The cubic root of 21553649 is about 278.2959815375.

The spelling of 21553649 in words is "twenty-one million, five hundred fifty-three thousand, six hundred forty-nine".