21649211 has 4 divisors (see below), whose sum is σ = 22922712. Its totient is φ = 20375712.

The previous prime is 21649207. The next prime is 21649219. The reversal of 21649211 is 11294612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21649211 - 2² = 21649207 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21649219) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 636725 + ... + 636758.

It is an arithmetic number, because the mean of its divisors is an integer number (5730678).

Almost surely, 2^21649211 is an apocalyptic number.

21649211 is a deficient number, since it is larger than the sum of its proper divisors (1273501).

21649211 is a wasteful number, since it uses less digits than its factorization.

21649211 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1273500.

The product of its digits is 864, while the sum is 26.

The square root of 21649211 is about 4652.8712640691. The cubic root of 21649211 is about 278.7066670359.

The spelling of 21649211 in words is "twenty-one million, six hundred forty-nine thousand, two hundred eleven".