21545039 has 2 divisors, whose sum is σ = 21545040. Its totient is φ = 21545038.

The previous prime is 21545011. The next prime is 21545047. The reversal of 21545039 is 93054512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21545039 - 2²⁴ = 4767823 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21545009) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10772519 + 10772520.

It is an arithmetic number, because the mean of its divisors is an integer number (10772520).

Almost surely, 2^21545039 is an apocalyptic number.

21545039 is a deficient number, since it is larger than the sum of its proper divisors (1).

21545039 is an equidigital number, since it uses as much as digits as its factorization.

21545039 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5400, while the sum is 29.

The square root of 21545039 is about 4641.6633871921. The cubic root of 21545039 is about 278.2589197925.

It can be divided in two parts, 2154503 and 9, that added together give a palindrome (2154512).

The spelling of 21545039 in words is "twenty-one million, five hundred forty-five thousand, thirty-nine".