21958817 has 2 divisors, whose sum is σ = 21958818. Its totient is φ = 21958816.

The previous prime is 21958799. The next prime is 21958831. The reversal of 21958817 is 71885912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21446161 + 512656 = 4631^2 + 716^2 .

It is a cyclic number.

It is not a de Polignac number, because 21958817 - 2¹⁶ = 21893281 is a prime.

It is not a weakly prime, because it can be changed into another prime (21958837) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10979408 + 10979409.

It is an arithmetic number, because the mean of its divisors is an integer number (10979409).

Almost surely, 2^21958817 is an apocalyptic number.

It is an amenable number.

21958817 is a deficient number, since it is larger than the sum of its proper divisors (1).

21958817 is an equidigital number, since it uses as much as digits as its factorization.

21958817 is an evil number, because the sum of its binary digits is even.

The product of its digits is 40320, while the sum is 41.

The square root of 21958817 is about 4686.0235808199. The cubic root of 21958817 is about 280.0289808438.

The spelling of 21958817 in words is "twenty-one million, nine hundred fifty-eight thousand, eight hundred seventeen".