21661353004607 has 4 divisors (see below), whose sum is σ = 21668258125056. Its totient is φ = 21654447884160.

The previous prime is 21661353004553. The next prime is 21661353004619. The reversal of 21661353004607 is 70640035316612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21661353004607 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 (21661353004667) 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, 3452555519 + ... + 3452561792.

It is an arithmetic number, because the mean of its divisors is an integer number (5417064531264).

Almost surely, 2^{21661353004607} is an apocalyptic number.

21661353004607 is a deficient number, since it is larger than the sum of its proper divisors (6905120449).

21661353004607 is an equidigital number, since it uses as much as digits as its factorization.

21661353004607 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6905120448.

The product of its (nonzero) digits is 544320, while the sum is 44.

The spelling of 21661353004607 in words is "twenty-one trillion, six hundred sixty-one billion, three hundred fifty-three million, four thousand, six hundred seven".