21455537 has 2 divisors, whose sum is σ = 21455538. Its totient is φ = 21455536.

The previous prime is 21455521. The next prime is 21455543. The reversal of 21455537 is 73555412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13184161 + 8271376 = 3631^2 + 2876^2 .

It is a cyclic number.

It is not a de Polignac number, because 21455537 - 2⁴ = 21455521 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21455557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10727768 + 10727769.

It is an arithmetic number, because the mean of its divisors is an integer number (10727769).

Almost surely, 2^21455537 is an apocalyptic number.

It is an amenable number.

21455537 is a deficient number, since it is larger than the sum of its proper divisors (1).

21455537 is an equidigital number, since it uses as much as digits as its factorization.

21455537 is an evil number, because the sum of its binary digits is even.

The product of its digits is 21000, while the sum is 32.

The square root of 21455537 is about 4632.0121977387. The cubic root of 21455537 is about 277.8730723297.

The spelling of 21455537 in words is "twenty-one million, four hundred fifty-five thousand, five hundred thirty-seven".