21427997 has 2 divisors, whose sum is σ = 21427998. Its totient is φ = 21427996.

The previous prime is 21427961. The next prime is 21428003. The reversal of 21427997 is 79972412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11978521 + 9449476 = 3461^2 + 3074^2 .

It is a cyclic number.

It is not a de Polignac number, because 21427997 - 2¹⁰ = 21426973 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21427097) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10713998 + 10713999.

It is an arithmetic number, because the mean of its divisors is an integer number (10713999).

Almost surely, 2^21427997 is an apocalyptic number.

It is an amenable number.

21427997 is a deficient number, since it is larger than the sum of its proper divisors (1).

21427997 is an equidigital number, since it uses as much as digits as its factorization.

21427997 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 63504, while the sum is 41.

The square root of 21427997 is about 4629.0384530699. The cubic root of 21427997 is about 277.7541302121.

The spelling of 21427997 in words is "twenty-one million, four hundred twenty-seven thousand, nine hundred ninety-seven".