21369640 has 16 divisors (see below), whose sum is σ = 48081780. Its totient is φ = 8547840.

The previous prime is 21369617. The next prime is 21369659. The reversal of 21369640 is 4696312.

It can be written as a sum of positive squares in 2 ways, for example, as 20848356 + 521284 = 4566^2 + 722^2 .

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, 267081 + ... + 267160.

Almost surely, 2^21369640 is an apocalyptic number.

21369640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21369640 is an abundant number, since it is smaller than the sum of its proper divisors (26712140).

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

21369640 is a wasteful number, since it uses less digits than its factorization.

21369640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 534252 (or 534248 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 31.

The square root of 21369640 is about 4622.7307946710. The cubic root of 21369640 is about 277.5017557988.

The spelling of 21369640 in words is "twenty-one million, three hundred sixty-nine thousand, six hundred forty".