21520061 has 2 divisors, whose sum is σ = 21520062. Its totient is φ = 21520060.

The previous prime is 21520021. The next prime is 21520069. The reversal of 21520061 is 16002512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21335161 + 184900 = 4619^2 + 430^2 .

It is a cyclic number.

It is not a de Polignac number, because 21520061 - 2²² = 17325757 is a prime.

It is a super-2 number, since 2×21520061² = 926226050887442, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21520069) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10760030 + 10760031.

It is an arithmetic number, because the mean of its divisors is an integer number (10760031).

Almost surely, 2^21520061 is an apocalyptic number.

It is an amenable number.

21520061 is a deficient number, since it is larger than the sum of its proper divisors (1).

21520061 is an equidigital number, since it uses as much as digits as its factorization.

21520061 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 120, while the sum is 17.

The square root of 21520061 is about 4638.9719766345. The cubic root of 21520061 is about 278.1513460882.

Adding to 21520061 its reverse (16002512), we get a palindrome (37522573).

The spelling of 21520061 in words is "twenty-one million, five hundred twenty thousand, sixty-one".