21656974429 has 2 divisors, whose sum is σ = 21656974430. Its totient is φ = 21656974428.

The previous prime is 21656974397. The next prime is 21656974453. The reversal of 21656974429 is 92447965612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19602800100 + 2054174329 = 140010^2 + 45323^2 .

It is a cyclic number.

It is not a de Polignac number, because 21656974429 - 2⁵ = 21656974397 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21656974429.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21656974499) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10828487214 + 10828487215.

It is an arithmetic number, because the mean of its divisors is an integer number (10828487215).

Almost surely, 2^21656974429 is an apocalyptic number.

It is an amenable number.

21656974429 is a deficient number, since it is larger than the sum of its proper divisors (1).

21656974429 is an equidigital number, since it uses as much as digits as its factorization.

21656974429 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6531840, while the sum is 55.

The spelling of 21656974429 in words is "twenty-one billion, six hundred fifty-six million, nine hundred seventy-four thousand, four hundred twenty-nine".