21153947 has 2 divisors, whose sum is σ = 21153948. Its totient is φ = 21153946.

The previous prime is 21153941. The next prime is 21153959. The reversal of 21153947 is 74935112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21153947 - 2⁴ = 21153931 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21153941) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10576973 + 10576974.

It is an arithmetic number, because the mean of its divisors is an integer number (10576974).

Almost surely, 2^21153947 is an apocalyptic number.

21153947 is a deficient number, since it is larger than the sum of its proper divisors (1).

21153947 is an equidigital number, since it uses as much as digits as its factorization.

21153947 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7560, while the sum is 32.

The square root of 21153947 is about 4599.3420181587. The cubic root of 21153947 is about 276.5649484946.

The spelling of 21153947 in words is "twenty-one million, one hundred fifty-three thousand, nine hundred forty-seven".