16721649 has 12 divisors (see below), whose sum is σ = 27604096. Its totient is φ = 9555192.

The previous prime is 16721647. The next prime is 16721651. The reversal of 16721649 is 94612761.

16721649 is a `hidden beast` number, since 1 + 6 + 7 + 2 + 1 + 649 = 666.

It is an interprime number because it is at equal distance from previous prime (16721647) and next prime (16721651).

It is not a de Polignac number, because 16721649 - 2¹ = 16721647 is a prime.

It is a super-2 number, since 2×16721649² = 559227090558402, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (16721641) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 132649 + ... + 132774.

Almost surely, 2^16721649 is an apocalyptic number.

It is an amenable number.

16721649 is a deficient number, since it is larger than the sum of its proper divisors (10882447).

16721649 is a wasteful number, since it uses less digits than its factorization.

16721649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 265436 (or 265433 counting only the distinct ones).

The product of its digits is 18144, while the sum is 36.

The square root of 16721649 is about 4089.2112931469. The cubic root of 16721649 is about 255.7170590208.

It can be divided in two parts, 1672 and 1649, that added together give a triangular number (3321 = T₈₁).

The spelling of 16721649 in words is "sixteen million, seven hundred twenty-one thousand, six hundred forty-nine".