21157610213 has 4 divisors (see below), whose sum is σ = 21203505708. Its totient is φ = 21111714720.

The previous prime is 21157610171. The next prime is 21157610249. The reversal of 21157610213 is 31201675112.

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 13161137284 + 7996472929 = 114722^2 + 89423^2 .

It is a cyclic number.

It is not a de Polignac number, because 21157610213 - 2¹² = 21157606117 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 (21157610813) 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, 22947056 + ... + 22947977.

It is an arithmetic number, because the mean of its divisors is an integer number (5300876427).

Almost surely, 2^21157610213 is an apocalyptic number.

It is an amenable number.

21157610213 is a deficient number, since it is larger than the sum of its proper divisors (45895495).

21157610213 is an equidigital number, since it uses as much as digits as its factorization.

21157610213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45895494.

The product of its (nonzero) digits is 2520, while the sum is 29.

The spelling of 21157610213 in words is "twenty-one billion, one hundred fifty-seven million, six hundred ten thousand, two hundred thirteen".