21697494 has 64 divisors (see below), whose sum is σ = 54566400. Its totient is φ = 5715360.

The previous prime is 21697477. The next prime is 21697531. The reversal of 21697494 is 49479612.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 26349 + ... + 27159.

It is an arithmetic number, because the mean of its divisors is an integer number (852600).

Almost surely, 2^21697494 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21697494, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27283200).

21697494 is an abundant number, since it is smaller than the sum of its proper divisors (32868906).

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

21697494 is a wasteful number, since it uses less digits than its factorization.

21697494 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 850 (or 836 counting only the distinct ones).

The product of its digits is 108864, while the sum is 42.

The square root of 21697494 is about 4658.0568910223. The cubic root of 21697494 is about 278.9137077206.

The spelling of 21697494 in words is "twenty-one million, six hundred ninety-seven thousand, four hundred ninety-four".