21378290 has 8 divisors (see below), whose sum is σ = 38480940. Its totient is φ = 8551312.

The previous prime is 21378289. The next prime is 21378317. The reversal of 21378290 is 9287312.

It can be written as a sum of positive squares in 2 ways, for example, as 21353641 + 24649 = 4621^2 + 157^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1068905 + ... + 1068924.

Almost surely, 2^21378290 is an apocalyptic number.

21378290 is a deficient number, since it is larger than the sum of its proper divisors (17102650).

21378290 is a wasteful number, since it uses less digits than its factorization.

21378290 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2137836.

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

The square root of 21378290 is about 4623.6662941869. Note that the first 3 decimals coincide. The cubic root of 21378290 is about 277.5391931224.

The spelling of 21378290 in words is "twenty-one million, three hundred seventy-eight thousand, two hundred ninety".