21697487 has 32 divisors (see below), whose sum is σ = 28062720. Its totient is φ = 16346880.

The previous prime is 21697477. The next prime is 21697531. The reversal of 21697487 is 78479612.

It is a cyclic number.

It is not a de Polignac number, because 21697487 - 2¹² = 21693391 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21697477) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 125333 + ... + 125505.

It is an arithmetic number, because the mean of its divisors is an integer number (876960).

Almost surely, 2^21697487 is an apocalyptic number.

21697487 is a deficient number, since it is larger than the sum of its proper divisors (6365233).

21697487 is a wasteful number, since it uses less digits than its factorization.

21697487 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 263.

The product of its digits is 169344, while the sum is 44.

The square root of 21697487 is about 4658.0561396359. The cubic root of 21697487 is about 278.9136777264.

The spelling of 21697487 in words is "twenty-one million, six hundred ninety-seven thousand, four hundred eighty-seven".