21397560 has 96 divisors (see below), whose sum is σ = 68301360. Its totient is φ = 5361664.

The previous prime is 21397559. The next prime is 21397573. The reversal of 21397560 is 6579312.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 34372 + ... + 34988.

Almost surely, 2^21397560 is an apocalyptic number.

21397560 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21397560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34150680).

21397560 is an abundant number, since it is smaller than the sum of its proper divisors (46903800).

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

21397560 is a wasteful number, since it uses less digits than its factorization.

21397560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 665 (or 644 counting only the distinct ones).

The product of its (nonzero) digits is 11340, while the sum is 33.

The square root of 21397560 is about 4625.7496689726. The cubic root of 21397560 is about 277.6225576655.

The spelling of 21397560 in words is "twenty-one million, three hundred ninety-seven thousand, five hundred sixty".