21747105961 has 9 divisors (see below), whose sum is σ = 25298854749. Its totient is φ = 18639491724.

The previous prime is 21747105917. The next prime is 21747105971. The reversal of 21747105961 is 16950174712.

It is a happy number.

The square root of 21747105961 is 147469.

It is a perfect power (a square), and thus also a powerful number.

It is not a de Polignac number, because 21747105961 - 2¹¹ = 21747103913 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21747105911) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 1021750 + ... + 1042816.

It is an arithmetic number, because the mean of its divisors is an integer number (2810983861).

Almost surely, 2^21747105961 is an apocalyptic number.

21747105961 is the 147469-th square number.

21747105961 is the 73735-th centered octagonal number.

It is an amenable number.

21747105961 is a deficient number, since it is larger than the sum of its proper divisors (3551748788).

21747105961 is an frugal number, since it uses more digits than its factorization.

21747105961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42148 (or 21074 counting only the distinct ones).

The product of its (nonzero) digits is 105840, while the sum is 43.

The spelling of 21747105961 in words is "twenty-one billion, seven hundred forty-seven million, one hundred five thousand, nine hundred sixty-one".