21661236202405 has 16 divisors (see below), whose sum is σ = 26684981697024. Its totient is φ = 16869815867520.

The previous prime is 21661236202391. The next prime is 21661236202477. The reversal of 21661236202405 is 50420263216612.

It is a happy number.

It is not a de Polignac number, because 21661236202405 - 2²¹ = 21661234105253 is a prime.

It is a super-2 number, since 2×21661236202405² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 114013689 + ... + 114203518.

It is an arithmetic number, because the mean of its divisors is an integer number (1667811356064).

Almost surely, 2^{21661236202405} is an apocalyptic number.

It is an amenable number.

21661236202405 is a deficient number, since it is larger than the sum of its proper divisors (5023745494619).

21661236202405 is a wasteful number, since it uses less digits than its factorization.

21661236202405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 228217716.

The product of its (nonzero) digits is 207360, while the sum is 40.

The spelling of 21661236202405 in words is "twenty-one trillion, six hundred sixty-one billion, two hundred thirty-six million, two hundred two thousand, four hundred five".