21878419 has 2 divisors, whose sum is σ = 21878420. Its totient is φ = 21878418.

The previous prime is 21878413. The next prime is 21878429. The reversal of 21878419 is 91487812.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21878419 - 2³ = 21878411 is a prime.

It is a super-2 number, since 2×21878419² = 957330435879122, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21878411) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10939209 + 10939210.

It is an arithmetic number, because the mean of its divisors is an integer number (10939210).

Almost surely, 2^21878419 is an apocalyptic number.

21878419 is a deficient number, since it is larger than the sum of its proper divisors (1).

21878419 is an equidigital number, since it uses as much as digits as its factorization.

21878419 is an evil number, because the sum of its binary digits is even.

The product of its digits is 32256, while the sum is 40.

The square root of 21878419 is about 4677.4372256611. The cubic root of 21878419 is about 279.6868054184.

The spelling of 21878419 in words is "twenty-one million, eight hundred seventy-eight thousand, four hundred nineteen".