21090061 has 2 divisors, whose sum is σ = 21090062. Its totient is φ = 21090060.

The previous prime is 21090007. The next prime is 21090067. The reversal of 21090061 is 16009012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19527561 + 1562500 = 4419^2 + 1250^2 .

It is a cyclic number.

It is not a de Polignac number, because 21090061 - 2¹¹ = 21088013 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21090067) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10545030 + 10545031.

It is an arithmetic number, because the mean of its divisors is an integer number (10545031).

Almost surely, 2^21090061 is an apocalyptic number.

It is an amenable number.

21090061 is a deficient number, since it is larger than the sum of its proper divisors (1).

21090061 is an equidigital number, since it uses as much as digits as its factorization.

21090061 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 108, while the sum is 19.

The square root of 21090061 is about 4592.3916427064. The cubic root of 21090061 is about 276.2862543275.

Adding to 21090061 its reverse (16009012), we get a palindrome (37099073).

The spelling of 21090061 in words is "twenty-one million, ninety thousand, sixty-one".