21057646 has 8 divisors (see below), whose sum is σ = 31656960. Its totient is φ = 10505328.

The previous prime is 21057623. The next prime is 21057661. The reversal of 21057646 is 64675012.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×21057646² = 886848910122632, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10606 + ... + 12433.

It is an arithmetic number, because the mean of its divisors is an integer number (3957120).

Almost surely, 2^21057646 is an apocalyptic number.

21057646 is a deficient number, since it is larger than the sum of its proper divisors (10599314).

21057646 is a wasteful number, since it uses less digits than its factorization.

21057646 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23498.

The product of its (nonzero) digits is 10080, while the sum is 31.

The square root of 21057646 is about 4588.8610787427. The cubic root of 21057646 is about 276.1446329391.

It can be divided in two parts, 210 and 57646, that multiplied together give a triangular number (12105660 = T₄₉₂₀).

The spelling of 21057646 in words is "twenty-one million, fifty-seven thousand, six hundred forty-six".