21511013 has 2 divisors, whose sum is σ = 21511014. Its totient is φ = 21511012.

The previous prime is 21510997. The next prime is 21511031. The reversal of 21511013 is 31011512.

Together with next prime (21511031) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19918369 + 1592644 = 4463^2 + 1262^2 .

It is a cyclic number.

It is not a de Polignac number, because 21511013 - 2⁴ = 21510997 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21511093) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10755506 + 10755507.

It is an arithmetic number, because the mean of its divisors is an integer number (10755507).

Almost surely, 2^21511013 is an apocalyptic number.

It is an amenable number.

21511013 is a deficient number, since it is larger than the sum of its proper divisors (1).

21511013 is an equidigital number, since it uses as much as digits as its factorization.

21511013 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 30, while the sum is 14.

The square root of 21511013 is about 4637.9966580411. The cubic root of 21511013 is about 278.1123581848.

Adding to 21511013 its reverse (31011512), we get a palindrome (52522525).

The spelling of 21511013 in words is "twenty-one million, five hundred eleven thousand, thirteen".