21657602749 has 2 divisors, whose sum is σ = 21657602750. Its totient is φ = 21657602748.

The previous prime is 21657602719. The next prime is 21657602753. The reversal of 21657602749 is 94720675612.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21636350649 + 21252100 = 147093^2 + 4610^2 .

It is a cyclic number.

It is not a de Polignac number, because 21657602749 - 2¹³ = 21657594557 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21657602719) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10828801374 + 10828801375.

It is an arithmetic number, because the mean of its divisors is an integer number (10828801375).

Almost surely, 2^21657602749 is an apocalyptic number.

It is an amenable number.

21657602749 is a deficient number, since it is larger than the sum of its proper divisors (1).

21657602749 is an equidigital number, since it uses as much as digits as its factorization.

21657602749 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1270080, while the sum is 49.

The spelling of 21657602749 in words is "twenty-one billion, six hundred fifty-seven million, six hundred two thousand, seven hundred forty-nine".