21642007205 has 32 divisors (see below), whose sum is σ = 33353316864. Its totient is φ = 13103076096.

The previous prime is 21642007193. The next prime is 21642007207. The reversal of 21642007205 is 50270024612.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21642007205 - 2⁶ = 21642007141 is a prime.

It is a super-2 number, since 2×21642007205² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21642007207) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1023554 + ... + 1044483.

It is an arithmetic number, because the mean of its divisors is an integer number (1042291152).

Almost surely, 2^21642007205 is an apocalyptic number.

It is an amenable number.

21642007205 is a deficient number, since it is larger than the sum of its proper divisors (11711309659).

21642007205 is a wasteful number, since it uses less digits than its factorization.

21642007205 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2068085.

The product of its (nonzero) digits is 6720, while the sum is 29.

The spelling of 21642007205 in words is "twenty-one billion, six hundred forty-two million, seven thousand, two hundred five".