21409720 has 16 divisors (see below), whose sum is σ = 48171960. Its totient is φ = 8563872.

The previous prime is 21409699. The next prime is 21409727. The reversal of 21409720 is 2790412.

It is a super-2 number, since 2×21409720² = 916752220956800, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21409727) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 267582 + ... + 267661.

Almost surely, 2^21409720 is an apocalyptic number.

21409720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21409720 is an abundant number, since it is smaller than the sum of its proper divisors (26762240).

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

21409720 is a wasteful number, since it uses less digits than its factorization.

21409720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 535254 (or 535250 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 25.

The square root of 21409720 is about 4627.0638638342. The cubic root of 21409720 is about 277.6751376639.

The spelling of 21409720 in words is "twenty-one million, four hundred nine thousand, seven hundred twenty".