21513929 has 2 divisors, whose sum is σ = 21513930. Its totient is φ = 21513928.

The previous prime is 21513893. The next prime is 21513931. The reversal of 21513929 is 92931512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19784704 + 1729225 = 4448^2 + 1315^2 .

It is a cyclic number.

It is not a de Polignac number, because 21513929 - 2²⁰ = 20465353 is a prime.

Together with 21513931, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21513895 and 21513904.

It is not a weakly prime, because it can be changed into another prime (21513949) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10756964 + 10756965.

It is an arithmetic number, because the mean of its divisors is an integer number (10756965).

Almost surely, 2^21513929 is an apocalyptic number.

It is an amenable number.

21513929 is a deficient number, since it is larger than the sum of its proper divisors (1).

21513929 is an equidigital number, since it uses as much as digits as its factorization.

21513929 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4860, while the sum is 32.

The square root of 21513929 is about 4638.3110072525. The cubic root of 21513929 is about 278.1249244455.

The spelling of 21513929 in words is "twenty-one million, five hundred thirteen thousand, nine hundred twenty-nine".