20991430 has 16 divisors (see below), whose sum is σ = 40007520. Its totient is φ = 7902592.

The previous prime is 20991427. The next prime is 20991431. The reversal of 20991430 is 3419902.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20991431) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 61570 + ... + 61909.

It is an arithmetic number, because the mean of its divisors is an integer number (2500470).

Almost surely, 2^20991430 is an apocalyptic number.

20991430 is a deficient number, since it is larger than the sum of its proper divisors (19016090).

20991430 is a wasteful number, since it uses less digits than its factorization.

20991430 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 123503.

The product of its (nonzero) digits is 1944, while the sum is 28.

The square root of 20991430 is about 4581.6405358780. The cubic root of 20991430 is about 275.8548824044.

The spelling of 20991430 in words is "twenty million, nine hundred ninety-one thousand, four hundred thirty".