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BaseRepresentation
bin10011111110111110…
…111000010000101101
32001101102120102110122
4103332332320100231
5322421141443141
613505122214325
71356512665601
oct237676702055
961342512418
1021457765421
119111392834
1241aa1b43a5
13203c700221
141077b53501
15858c2164b
hex4fefb842d

21457765421 has 2 divisors, whose sum is σ = 21457765422. Its totient is φ = 21457765420.

The previous prime is 21457765403. The next prime is 21457765531. The reversal of 21457765421 is 12456775412.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21065329321 + 392436100 = 145139^2 + 19810^2 .

It is a cyclic number.

It is not a de Polignac number, because 21457765421 - 226 = 21390656557 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21457761421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10728882710 + 10728882711.

It is an arithmetic number, because the mean of its divisors is an integer number (10728882711).

Almost surely, 221457765421 is an apocalyptic number.

It is an amenable number.

21457765421 is a deficient number, since it is larger than the sum of its proper divisors (1).

21457765421 is an equidigital number, since it uses as much as digits as its factorization.

21457765421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 470400, while the sum is 44.

Subtracting from 21457765421 its reverse (12456775412), we obtain a palindrome (9000990009).

The spelling of 21457765421 in words is "twenty-one billion, four hundred fifty-seven million, seven hundred sixty-five thousand, four hundred twenty-one".