21577658461 has 4 divisors (see below), whose sum is σ = 21581417500. Its totient is φ = 21573899424.

The previous prime is 21577658447. The next prime is 21577658491. The reversal of 21577658461 is 16485677512.

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 9076182361 + 12501476100 = 95269^2 + 111810^2 .

It is a cyclic number.

It is not a de Polignac number, because 21577658461 - 2⁵ = 21577658429 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21577658399 and 21577658408.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21577658441) 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, 1870896 + ... + 1882393.

It is an arithmetic number, because the mean of its divisors is an integer number (5395354375).

Almost surely, 2^21577658461 is an apocalyptic number.

It is an amenable number.

21577658461 is a deficient number, since it is larger than the sum of its proper divisors (3759039).

21577658461 is an equidigital number, since it uses as much as digits as its factorization.

21577658461 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3759038.

The product of its digits is 2822400, while the sum is 52.

The spelling of 21577658461 in words is "twenty-one billion, five hundred seventy-seven million, six hundred fifty-eight thousand, four hundred sixty-one".