21340537 has 2 divisors, whose sum is σ = 21340538. Its totient is φ = 21340536.

The previous prime is 21340523. The next prime is 21340547. The reversal of 21340537 is 73504312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13920361 + 7420176 = 3731^2 + 2724^2 .

It is a cyclic number.

It is not a de Polignac number, because 21340537 - 2⁷ = 21340409 is a prime.

It is not a weakly prime, because it can be changed into another prime (21340547) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10670268 + 10670269.

It is an arithmetic number, because the mean of its divisors is an integer number (10670269).

Almost surely, 2^21340537 is an apocalyptic number.

It is an amenable number.

21340537 is a deficient number, since it is larger than the sum of its proper divisors (1).

21340537 is an equidigital number, since it uses as much as digits as its factorization.

21340537 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2520, while the sum is 25.

The square root of 21340537 is about 4619.5819074890. The cubic root of 21340537 is about 277.3757233741.

Adding to 21340537 its reverse (73504312), we get a palindrome (94844849).

The spelling of 21340537 in words is "twenty-one million, three hundred forty thousand, five hundred thirty-seven".