21661165732428 has 36 divisors (see below), whose sum is σ = 54806711108968. Its totient is φ = 7213518547200.

The previous prime is 21661165732387. The next prime is 21661165732429. The reversal of 21661165732428 is 82423756116612.

21661165732428 is a `hidden beast` number, since 2 + 1 + 6 + 61 + 1 + 6 + 573 + 2 + 4 + 2 + 8 = 666.

It is a tau number, because it is divible by the number of its divisors (36).

It is a super-2 number, since 2×21661165732428² (a number of 27 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21661165732429) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 286212901 + ... + 286288572.

Almost surely, 2^{21661165732428} is an apocalyptic number.

It is an amenable number.

21661165732428 is an abundant number, since it is smaller than the sum of its proper divisors (33145545376540).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21661165732428 is a wasteful number, since it uses less digits than its factorization.

21661165732428 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 572502534 (or 572502529 counting only the distinct ones).

The product of its digits is 5806080, while the sum is 54.

The spelling of 21661165732428 in words is "twenty-one trillion, six hundred sixty-one billion, one hundred sixty-five million, seven hundred thirty-two thousand, four hundred twenty-eight".