21513057 has 4 divisors (see below), whose sum is σ = 28684080. Its totient is φ = 14342036.

The previous prime is 21513049. The next prime is 21513061. The reversal of 21513057 is 75031512.

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 21513057 - 2³ = 21513049 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21513077) 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, 3585507 + ... + 3585512.

It is an arithmetic number, because the mean of its divisors is an integer number (7171020).

Almost surely, 2^21513057 is an apocalyptic number.

It is an amenable number.

21513057 is a deficient number, since it is larger than the sum of its proper divisors (7171023).

21513057 is an equidigital number, since it uses as much as digits as its factorization.

21513057 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7171022.

The product of its (nonzero) digits is 1050, while the sum is 24.

The square root of 21513057 is about 4638.2170065662. The cubic root of 21513057 is about 278.1211667527.

Adding to 21513057 its reverse (75031512), we get a palindrome (96544569).

The spelling of 21513057 in words is "twenty-one million, five hundred thirteen thousand, fifty-seven".