21528949 has 4 divisors (see below), whose sum is σ = 23185036. Its totient is φ = 19872864.

The previous prime is 21528937. The next prime is 21529003. The reversal of 21528949 is 94982512.

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 8439025 + 13089924 = 2905^2 + 3618^2 .

It is a cyclic number.

It is not a de Polignac number, because 21528949 - 2¹⁹ = 21004661 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 (21528929) 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, 828024 + ... + 828049.

It is an arithmetic number, because the mean of its divisors is an integer number (5796259).

Almost surely, 2^21528949 is an apocalyptic number.

It is an amenable number.

21528949 is a deficient number, since it is larger than the sum of its proper divisors (1656087).

21528949 is a wasteful number, since it uses less digits than its factorization.

21528949 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1656086.

The product of its digits is 51840, while the sum is 40.

The square root of 21528949 is about 4639.9298486076. The cubic root of 21528949 is about 278.1896339117.

The spelling of 21528949 in words is "twenty-one million, five hundred twenty-eight thousand, nine hundred forty-nine".