21612061 has 2 divisors, whose sum is σ = 21612062. Its totient is φ = 21612060.

The previous prime is 21612037. The next prime is 21612067. The reversal of 21612061 is 16021612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11689561 + 9922500 = 3419^2 + 3150^2 .

It is a cyclic number.

It is not a de Polignac number, because 21612061 - 2⁹ = 21611549 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21612067) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10806030 + 10806031.

It is an arithmetic number, because the mean of its divisors is an integer number (10806031).

Almost surely, 2^21612061 is an apocalyptic number.

It is an amenable number.

21612061 is a deficient number, since it is larger than the sum of its proper divisors (1).

21612061 is an equidigital number, since it uses as much as digits as its factorization.

21612061 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 144, while the sum is 19.

The square root of 21612061 is about 4648.8773913710. The cubic root of 21612061 is about 278.5471557449.

Adding to 21612061 its reverse (16021612), we get a palindrome (37633673).

The spelling of 21612061 in words is "twenty-one million, six hundred twelve thousand, sixty-one".