21507520213 has 4 divisors (see below), whose sum is σ = 21508069068. Its totient is φ = 21506971360.

The previous prime is 21507520169. The next prime is 21507520249. The reversal of 21507520213 is 31202570512.

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 10100853009 + 11406667204 = 100503^2 + 106802^2 .

It is a cyclic number.

It is not a de Polignac number, because 21507520213 - 2⁹ = 21507519701 is a prime.

It is a super-3 number, since 3×21507520213³ (a number of 32 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21507520253) 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, 210718 + ... + 295663.

It is an arithmetic number, because the mean of its divisors is an integer number (5377017267).

Almost surely, 2^21507520213 is an apocalyptic number.

It is an amenable number.

21507520213 is a deficient number, since it is larger than the sum of its proper divisors (548855).

21507520213 is an equidigital number, since it uses as much as digits as its factorization.

21507520213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 548854.

The product of its (nonzero) digits is 4200, while the sum is 28.

The spelling of 21507520213 in words is "twenty-one billion, five hundred seven million, five hundred twenty thousand, two hundred thirteen".