21121278 has 16 divisors (see below), whose sum is σ = 42287616. Its totient is φ = 7032920.

The previous prime is 21121277. The next prime is 21121319. The reversal of 21121278 is 87212112.

It is a super-2 number, since 2×21121278² = 892216768706568, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121271) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9973 + ... + 11903.

It is an arithmetic number, because the mean of its divisors is an integer number (2642976).

Almost surely, 2^21121278 is an apocalyptic number.

21121278 is an abundant number, since it is smaller than the sum of its proper divisors (21166338).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21121278 is a wasteful number, since it uses less digits than its factorization.

21121278 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3759.

The product of its digits is 448, while the sum is 24.

The square root of 21121278 is about 4595.7891596547. The cubic root of 21121278 is about 276.4225045431.

The spelling of 21121278 in words is "twenty-one million, one hundred twenty-one thousand, two hundred seventy-eight".