21091378 has 32 divisors (see below), whose sum is σ = 39748608. Its totient is φ = 8154000.

The previous prime is 21091361. The next prime is 21091409. The reversal of 21091378 is 87319012.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 22801 + ... + 23707.

It is an arithmetic number, because the mean of its divisors is an integer number (1242144).

Almost surely, 2^21091378 is an apocalyptic number.

21091378 is a deficient number, since it is larger than the sum of its proper divisors (18657230).

21091378 is a wasteful number, since it uses less digits than its factorization.

21091378 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1078.

The product of its (nonzero) digits is 3024, while the sum is 31.

The square root of 21091378 is about 4592.5350298065. The cubic root of 21091378 is about 276.2920052421.

The spelling of 21091378 in words is "twenty-one million, ninety-one thousand, three hundred seventy-eight".