21423424615661 has 2 divisors, whose sum is σ = 21423424615662. Its totient is φ = 21423424615660.

The previous prime is 21423424615631. The next prime is 21423424615771. The reversal of 21423424615661 is 16651642432412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16519192913161 + 4904231702500 = 4064381^2 + 2214550^2 .

It is a cyclic number.

It is not a de Polignac number, because 21423424615661 - 2⁶ = 21423424615597 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21423424615631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10711712307830 + 10711712307831.

It is an arithmetic number, because the mean of its divisors is an integer number (10711712307831).

Almost surely, 2^{21423424615661} is an apocalyptic number.

It is an amenable number.

21423424615661 is a deficient number, since it is larger than the sum of its proper divisors (1).

21423424615661 is an equidigital number, since it uses as much as digits as its factorization.

21423424615661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1658880, while the sum is 47.

The spelling of 21423424615661 in words is "twenty-one trillion, four hundred twenty-three billion, four hundred twenty-four million, six hundred fifteen thousand, six hundred sixty-one".