21352778 has 8 divisors (see below), whose sum is σ = 32181600. Its totient is φ = 10625580.

The previous prime is 21352733. The next prime is 21352781. The reversal of 21352778 is 87725312.

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

It is a super-2 number, since 2×21352778² = 911882256634568, which contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 24878 + ... + 25721.

It is an arithmetic number, because the mean of its divisors is an integer number (4022700).

Almost surely, 2^21352778 is an apocalyptic number.

21352778 is a deficient number, since it is larger than the sum of its proper divisors (10828822).

21352778 is a wasteful number, since it uses less digits than its factorization.

21352778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50812.

The product of its digits is 23520, while the sum is 35.

The square root of 21352778 is about 4620.9066209998. The cubic root of 21352778 is about 277.4287477699.

It can be divided in two parts, 213527 and 78, that multiplied together give a triangular number (16655106 = T₅₇₇₁).

The spelling of 21352778 in words is "twenty-one million, three hundred fifty-two thousand, seven hundred seventy-eight".