21265537 has 2 divisors, whose sum is σ = 21265538. Its totient is φ = 21265536.

The previous prime is 21265529. The next prime is 21265549. The reversal of 21265537 is 73556212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11587216 + 9678321 = 3404^2 + 3111^2 .

It is a cyclic number.

It is not a de Polignac number, because 21265537 - 2³ = 21265529 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21265499 and 21265508.

It is not a weakly prime, because it can be changed into another prime (21265577) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10632768 + 10632769.

It is an arithmetic number, because the mean of its divisors is an integer number (10632769).

Almost surely, 2^21265537 is an apocalyptic number.

It is an amenable number.

21265537 is a deficient number, since it is larger than the sum of its proper divisors (1).

21265537 is an equidigital number, since it uses as much as digits as its factorization.

21265537 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12600, while the sum is 31.

The square root of 21265537 is about 4611.4571449814. The cubic root of 21265537 is about 277.0504020159.

The spelling of 21265537 in words is "twenty-one million, two hundred sixty-five thousand, five hundred thirty-seven".