21949387 has 2 divisors, whose sum is σ = 21949388. Its totient is φ = 21949386.

The previous prime is 21949379. The next prime is 21949409. The reversal of 21949387 is 78394912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21949387 - 2³ = 21949379 is a prime.

It is not a weakly prime, because it can be changed into another prime (21949087) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10974693 + 10974694.

It is an arithmetic number, because the mean of its divisors is an integer number (10974694).

Almost surely, 2^21949387 is an apocalyptic number.

21949387 is a deficient number, since it is larger than the sum of its proper divisors (1).

21949387 is an equidigital number, since it uses as much as digits as its factorization.

21949387 is an evil number, because the sum of its binary digits is even.

The product of its digits is 108864, while the sum is 43.

The square root of 21949387 is about 4685.0172891890. The cubic root of 21949387 is about 279.9888898653.

The spelling of 21949387 in words is "twenty-one million, nine hundred forty-nine thousand, three hundred eighty-seven".