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21525000781 is a prime number
BaseRepresentation
bin10100000010111111…
…010111001001001101
32001120010002100001011
4110002333113021031
5323040400011111
613515523245221
71361260326214
oct240277271115
961503070034
1021525000781
119146335749
124208819811
13205061156b
141082a5607b
1585eaa3021
hex502fd724d

21525000781 has 2 divisors, whose sum is σ = 21525000782. Its totient is φ = 21525000780.

The previous prime is 21525000769. The next prime is 21525000787. The reversal of 21525000781 is 18700052512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16881804900 + 4643195881 = 129930^2 + 68141^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2k-21525000781 is a prime.

It is a super-2 number, since 2×215250007812 (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21525000787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10762500390 + 10762500391.

It is an arithmetic number, because the mean of its divisors is an integer number (10762500391).

Almost surely, 221525000781 is an apocalyptic number.

21525000781 is the 65613-rd centered decagonal number.

It is an amenable number.

21525000781 is a deficient number, since it is larger than the sum of its proper divisors (1).

21525000781 is an equidigital number, since it uses as much as digits as its factorization.

21525000781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5600, while the sum is 31.

The spelling of 21525000781 in words is "twenty-one billion, five hundred twenty-five million, seven hundred eighty-one", and thus it is an aban number.