21976421 has 2 divisors, whose sum is σ = 21976422. Its totient is φ = 21976420.

The previous prime is 21976399. The next prime is 21976433. The reversal of 21976421 is 12467912.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20376196 + 1600225 = 4514^2 + 1265^2 .

It is a cyclic number.

It is not a de Polignac number, because 21976421 - 2²² = 17782117 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 (21976441) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10988210 + 10988211.

It is an arithmetic number, because the mean of its divisors is an integer number (10988211).

Almost surely, 2^21976421 is an apocalyptic number.

It is an amenable number.

21976421 is a deficient number, since it is larger than the sum of its proper divisors (1).

21976421 is an equidigital number, since it uses as much as digits as its factorization.

21976421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6048, while the sum is 32.

The square root of 21976421 is about 4687.9015561336. The cubic root of 21976421 is about 280.1037923031.

The spelling of 21976421 in words is "twenty-one million, nine hundred seventy-six thousand, four hundred twenty-one".