21697340 has 24 divisors (see below), whose sum is σ = 52073952. Its totient is φ = 7439040.

The previous prime is 21697339. The next prime is 21697343. The reversal of 21697340 is 4379612.

It is a junction number, because it is equal to n+sod(n) for n = 21697297 and 21697306.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21697343) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 77351 + ... + 77630.

It is an arithmetic number, because the mean of its divisors is an integer number (2169748).

Almost surely, 2^21697340 is an apocalyptic number.

21697340 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21697340 is an abundant number, since it is smaller than the sum of its proper divisors (30376612).

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

21697340 is a wasteful number, since it uses less digits than its factorization.

21697340 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 154997 (or 154995 counting only the distinct ones).

The product of its (nonzero) digits is 9072, while the sum is 32.

The square root of 21697340 is about 4658.0403604950. The cubic root of 21697340 is about 278.9130478470.

The spelling of 21697340 in words is "twenty-one million, six hundred ninety-seven thousand, three hundred forty".