21521149 has 4 divisors (see below), whose sum is σ = 23176636. Its totient is φ = 19865664.

The previous prime is 21521141. The next prime is 21521183. The reversal of 21521149 is 94112512.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 9721924 + 11799225 = 3118^2 + 3435^2 .

It is not a de Polignac number, because 21521149 - 2³ = 21521141 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 (21521141) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 827724 + ... + 827749.

It is an arithmetic number, because the mean of its divisors is an integer number (5794159).

Almost surely, 2^21521149 is an apocalyptic number.

It is an amenable number.

21521149 is a deficient number, since it is larger than the sum of its proper divisors (1655487).

21521149 is a wasteful number, since it uses less digits than its factorization.

21521149 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1655486.

The product of its digits is 720, while the sum is 25.

The square root of 21521149 is about 4639.0892425130. The cubic root of 21521149 is about 278.1560335526.

The spelling of 21521149 in words is "twenty-one million, five hundred twenty-one thousand, one hundred forty-nine".