21564149 has 2 divisors, whose sum is σ = 21564150. Its totient is φ = 21564148.

The previous prime is 21564131. The next prime is 21564181. The reversal of 21564149 is 94146512.

It is an a-pointer prime, because the next prime (21564181) can be obtained adding 21564149 to its sum of digits (32).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10956100 + 10608049 = 3310^2 + 3257^2 .

It is a cyclic number.

It is not a de Polignac number, because 21564149 - 2¹² = 21560053 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21564349) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10782074 + 10782075.

It is an arithmetic number, because the mean of its divisors is an integer number (10782075).

Almost surely, 2^21564149 is an apocalyptic number.

It is an amenable number.

21564149 is a deficient number, since it is larger than the sum of its proper divisors (1).

21564149 is an equidigital number, since it uses as much as digits as its factorization.

21564149 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8640, while the sum is 32.

The square root of 21564149 is about 4643.7214602084. The cubic root of 21564149 is about 278.3411654323.

The spelling of 21564149 in words is "twenty-one million, five hundred sixty-four thousand, one hundred forty-nine".