21520949 has 2 divisors, whose sum is σ = 21520950. Its totient is φ = 21520948.

The previous prime is 21520931. The next prime is 21520999. The reversal of 21520949 is 94902512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19518724 + 2002225 = 4418^2 + 1415^2 .

It is a cyclic number.

It is not a de Polignac number, because 21520949 - 2⁸ = 21520693 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21520999) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10760474 + 10760475.

It is an arithmetic number, because the mean of its divisors is an integer number (10760475).

Almost surely, 2^21520949 is an apocalyptic number.

It is an amenable number.

21520949 is a deficient number, since it is larger than the sum of its proper divisors (1).

21520949 is an equidigital number, since it uses as much as digits as its factorization.

21520949 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6480, while the sum is 32.

The square root of 21520949 is about 4639.0676865077. The cubic root of 21520949 is about 278.1551718982.

The spelling of 21520949 in words is "twenty-one million, five hundred twenty thousand, nine hundred forty-nine".