21697648 has 40 divisors (see below), whose sum is σ = 50139648. Its totient is φ = 8893632.

The previous prime is 21697633. The next prime is 21697657. The reversal of 21697648 is 84679612.

21697648 = T₁₄₂₇ + T₁₄₂₈ + ... + T₁₄₄₇.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1636 + ... + 6787.

Almost surely, 2^21697648 is an apocalyptic number.

21697648 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21697648 is an abundant number, since it is smaller than the sum of its proper divisors (28442000).

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

21697648 is a wasteful number, since it uses less digits than its factorization.

21697648 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8461 (or 8455 counting only the distinct ones).

The product of its digits is 145152, while the sum is 43.

The square root of 21697648 is about 4658.0734214909. The cubic root of 21697648 is about 278.9143675911.

The spelling of 21697648 in words is "twenty-one million, six hundred ninety-seven thousand, six hundred forty-eight".