20742581 has 2 divisors, whose sum is σ = 20742582. Its totient is φ = 20742580.

The previous prime is 20742563. The next prime is 20742583. The reversal of 20742581 is 18524702.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19722481 + 1020100 = 4441^2 + 1010^2 .

It is a cyclic number.

It is not a de Polignac number, because 20742581 - 2⁶ = 20742517 is a prime.

It is a super-2 number, since 2×20742581² = 860509333083122, which contains 22 as substring.

Together with 20742583, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20742583) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10371290 + 10371291.

It is an arithmetic number, because the mean of its divisors is an integer number (10371291).

Almost surely, 2^20742581 is an apocalyptic number.

It is an amenable number.

20742581 is a deficient number, since it is larger than the sum of its proper divisors (1).

20742581 is an equidigital number, since it uses as much as digits as its factorization.

20742581 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4480, while the sum is 29.

The square root of 20742581 is about 4554.4023757240. The cubic root of 20742581 is about 274.7604790446.

The spelling of 20742581 in words is "twenty million, seven hundred forty-two thousand, five hundred eighty-one".