21392778 has 32 divisors (see below), whose sum is σ = 48288960. Its totient is φ = 6258560.

The previous prime is 21392773. The next prime is 21392779. The reversal of 21392778 is 87729312.

It is not an unprimeable number, because it can be changed into a prime (21392773) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3675 + ... + 7502.

It is an arithmetic number, because the mean of its divisors is an integer number (1509030).

Almost surely, 2^21392778 is an apocalyptic number.

21392778 is an abundant number, since it is smaller than the sum of its proper divisors (26896182).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21392778 is a wasteful number, since it uses less digits than its factorization.

21392778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11222.

The product of its digits is 42336, while the sum is 39.

The square root of 21392778 is about 4625.2327509002. The cubic root of 21392778 is about 277.6018747780.

The spelling of 21392778 in words is "twenty-one million, three hundred ninety-two thousand, seven hundred seventy-eight".