21697140 has 48 divisors (see below), whose sum is σ = 61907328. Its totient is φ = 5675904.

The previous prime is 21697129. The next prime is 21697147. The reversal of 21697140 is 4179612.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 21697098 and 21697107.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21697147) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 232 + ... + 6591.

It is an arithmetic number, because the mean of its divisors is an integer number (1289736).

Almost surely, 2^21697140 is an apocalyptic number.

21697140 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 21697140, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30953664).

21697140 is an abundant number, since it is smaller than the sum of its proper divisors (40210188).

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

21697140 is a wasteful number, since it uses less digits than its factorization.

21697140 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6888 (or 6886 counting only the distinct ones).

The product of its (nonzero) digits is 3024, while the sum is 30.

The square root of 21697140 is about 4658.0188921901. The cubic root of 21697140 is about 278.9121908636.

The spelling of 21697140 in words is "twenty-one million, six hundred ninety-seven thousand, one hundred forty".