21521396 has 24 divisors (see below), whose sum is σ = 40942440. Its totient is φ = 9839232.

The previous prime is 21521389. The next prime is 21521413. The reversal of 21521396 is 69312512.

It can be written as a sum of positive squares in 4 ways, for example, as 28900 + 21492496 = 170^2 + 4636^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3770 + ... + 7566.

It is an arithmetic number, because the mean of its divisors is an integer number (1705935).

Almost surely, 2^21521396 is an apocalyptic number.

21521396 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

21521396 is a deficient number, since it is larger than the sum of its proper divisors (19421044).

21521396 is a wasteful number, since it uses less digits than its factorization.

21521396 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3923 (or 3921 counting only the distinct ones).

The product of its digits is 3240, while the sum is 29.

The square root of 21521396 is about 4639.1158640413. The cubic root of 21521396 is about 278.1570976885.

The spelling of 21521396 in words is "twenty-one million, five hundred twenty-one thousand, three hundred ninety-six".