21612222661 has 2 divisors, whose sum is σ = 21612222662. Its totient is φ = 21612222660.

The previous prime is 21612222641. The next prime is 21612222677. The reversal of 21612222661 is 16622221612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21460785025 + 151437636 = 146495^2 + 12306^2 .

It is a cyclic number.

It is not a de Polignac number, because 21612222661 - 2²³ = 21603834053 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21612222631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10806111330 + 10806111331.

It is an arithmetic number, because the mean of its divisors is an integer number (10806111331).

Almost surely, 2^21612222661 is an apocalyptic number.

It is an amenable number.

21612222661 is a deficient number, since it is larger than the sum of its proper divisors (1).

21612222661 is an equidigital number, since it uses as much as digits as its factorization.

21612222661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6912, while the sum is 31.

The spelling of 21612222661 in words is "twenty-one billion, six hundred twelve million, two hundred twenty-two thousand, six hundred sixty-one".