21531646 has 4 divisors (see below), whose sum is σ = 32297472. Its totient is φ = 10765822.

The previous prime is 21531641. The next prime is 21531649. The reversal of 21531646 is 64613512.

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

It is a super-2 number, since 2×21531646² = 927223558938632, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21531641) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5382910 + ... + 5382913.

It is an arithmetic number, because the mean of its divisors is an integer number (8074368).

Almost surely, 2^21531646 is an apocalyptic number.

21531646 is a deficient number, since it is larger than the sum of its proper divisors (10765826).

21531646 is a wasteful number, since it uses less digits than its factorization.

21531646 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10765825.

The product of its digits is 4320, while the sum is 28.

The square root of 21531646 is about 4640.2204689002. The cubic root of 21531646 is about 278.2012499937.

The spelling of 21531646 in words is "twenty-one million, five hundred thirty-one thousand, six hundred forty-six".