21694537 has 2 divisors, whose sum is σ = 21694538. Its totient is φ = 21694536.

The previous prime is 21694511. The next prime is 21694559. The reversal of 21694537 is 73549612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13278736 + 8415801 = 3644^2 + 2901^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21694537 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21694496 and 21694505.

It is not a weakly prime, because it can be changed into another prime (21694507) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10847268 + 10847269.

It is an arithmetic number, because the mean of its divisors is an integer number (10847269).

Almost surely, 2^21694537 is an apocalyptic number.

It is an amenable number.

21694537 is a deficient number, since it is larger than the sum of its proper divisors (1).

21694537 is an equidigital number, since it uses as much as digits as its factorization.

21694537 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 45360, while the sum is 37.

The square root of 21694537 is about 4657.7394731779. The cubic root of 21694537 is about 278.9010367442.

The spelling of 21694537 in words is "twenty-one million, six hundred ninety-four thousand, five hundred thirty-seven".