21137929 has 2 divisors, whose sum is σ = 21137930. Its totient is φ = 21137928.

The previous prime is 21137927. The next prime is 21137959. The reversal of 21137929 is 92973112.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13520329 + 7617600 = 3677^2 + 2760^2 .

It is a cyclic number.

It is not a de Polignac number, because 21137929 - 2¹ = 21137927 is a prime.

Together with 21137927, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21137894 and 21137903.

It is not a weakly prime, because it can be changed into another prime (21137923) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10568964 + 10568965.

It is an arithmetic number, because the mean of its divisors is an integer number (10568965).

Almost surely, 2^21137929 is an apocalyptic number.

It is an amenable number.

21137929 is a deficient number, since it is larger than the sum of its proper divisors (1).

21137929 is an equidigital number, since it uses as much as digits as its factorization.

21137929 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6804, while the sum is 34.

The square root of 21137929 is about 4597.6003523577. The cubic root of 21137929 is about 276.4951248668.

The spelling of 21137929 in words is "twenty-one million, one hundred thirty-seven thousand, nine hundred twenty-nine".