21602811655861 has 2 divisors, whose sum is σ = 21602811655862. Its totient is φ = 21602811655860.

The previous prime is 21602811655837. The next prime is 21602811655927. The reversal of 21602811655861 is 16855611820612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21492774160900 + 110037494961 = 4636030^2 + 331719^2 .

It is a cyclic number.

It is not a de Polignac number, because 21602811655861 - 2¹⁵ = 21602811623093 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21602811655799 and 21602811655808.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21602811655811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10801405827930 + 10801405827931.

It is an arithmetic number, because the mean of its divisors is an integer number (10801405827931).

Almost surely, 2^{21602811655861} is an apocalyptic number.

It is an amenable number.

21602811655861 is a deficient number, since it is larger than the sum of its proper divisors (1).

21602811655861 is an equidigital number, since it uses as much as digits as its factorization.

21602811655861 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1382400, while the sum is 52.

The spelling of 21602811655861 in words is "twenty-one trillion, six hundred two billion, eight hundred eleven million, six hundred fifty-five thousand, eight hundred sixty-one".