21971561513 has 24 divisors (see below), whose sum is σ = 24790345608. Its totient is φ = 19451520000.

The previous prime is 21971561489. The next prime is 21971561533. The reversal of 21971561513 is 31516517912.

It can be written as a sum of positive squares in 4 ways, for example, as 1292258704 + 20679302809 = 35948^2 + 143803^2 .

It is not a de Polignac number, because 21971561513 - 2¹⁴ = 21971545129 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21971561533) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 730745 + ... + 760217.

It is an arithmetic number, because the mean of its divisors is an integer number (1032931067).

Almost surely, 2^21971561513 is an apocalyptic number.

It is an amenable number.

21971561513 is a deficient number, since it is larger than the sum of its proper divisors (2818784095).

21971561513 is a wasteful number, since it uses less digits than its factorization.

21971561513 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29657 (or 29646 counting only the distinct ones).

The product of its digits is 56700, while the sum is 41.

The spelling of 21971561513 in words is "twenty-one billion, nine hundred seventy-one million, five hundred sixty-one thousand, five hundred thirteen".