21615379 has 2 divisors, whose sum is σ = 21615380. Its totient is φ = 21615378.

The previous prime is 21615359. The next prime is 21615409. The reversal of 21615379 is 97351612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21615379 - 2⁹ = 21614867 is a prime.

It is not a weakly prime, because it can be changed into another prime (21615359) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10807689 + 10807690.

It is an arithmetic number, because the mean of its divisors is an integer number (10807690).

Almost surely, 2^21615379 is an apocalyptic number.

21615379 is a deficient number, since it is larger than the sum of its proper divisors (1).

21615379 is an equidigital number, since it uses as much as digits as its factorization.

21615379 is an evil number, because the sum of its binary digits is even.

The product of its digits is 11340, while the sum is 34.

The square root of 21615379 is about 4649.2342380224. The cubic root of 21615379 is about 278.5614097020.

The spelling of 21615379 in words is "twenty-one million, six hundred fifteen thousand, three hundred seventy-nine".