21557149 has 4 divisors (see below), whose sum is σ = 21677760. Its totient is φ = 21436540.

The previous prime is 21557143. The next prime is 21557177. The reversal of 21557149 is 94175512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21557149 - 2²³ = 13168541 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21557143) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 60037 + ... + 60394.

It is an arithmetic number, because the mean of its divisors is an integer number (5419440).

Almost surely, 2^21557149 is an apocalyptic number.

It is an amenable number.

21557149 is a deficient number, since it is larger than the sum of its proper divisors (120611).

21557149 is a wasteful number, since it uses less digits than its factorization.

21557149 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 120610.

The product of its digits is 12600, while the sum is 34.

The square root of 21557149 is about 4642.9676931893. The cubic root of 21557149 is about 278.3110444660.

The spelling of 21557149 in words is "twenty-one million, five hundred fifty-seven thousand, one hundred forty-nine".