21581741 has 2 divisors, whose sum is σ = 21581742. Its totient is φ = 21581740.

The previous prime is 21581737. The next prime is 21581761. The reversal of 21581741 is 14718512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18028516 + 3553225 = 4246^2 + 1885^2 .

It is a cyclic number.

It is not a de Polignac number, because 21581741 - 2² = 21581737 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21581711) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10790870 + 10790871.

It is an arithmetic number, because the mean of its divisors is an integer number (10790871).

Almost surely, 2^21581741 is an apocalyptic number.

It is an amenable number.

21581741 is a deficient number, since it is larger than the sum of its proper divisors (1).

21581741 is an equidigital number, since it uses as much as digits as its factorization.

21581741 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2240, while the sum is 29.

The square root of 21581741 is about 4645.6152445074. The cubic root of 21581741 is about 278.4168349590.

It can be divided in two parts, 21581 and 741, that added together give a palindrome (22322).

The spelling of 21581741 in words is "twenty-one million, five hundred eighty-one thousand, seven hundred forty-one".